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REESE  LIBRARY 

OF  THK 

UNIVERSITY  OF  CALIFORNIA. 


,  igo 
^Accession  M > .       O  /£ t/  xJ < 3    .   Class  No . 


GALVANIZING 

AND  TINNING 


A  PRACTICAL  TREATISE  ON  COATING  WITH  TIN  AND  ZINC 

WITH   A 

SPECIAL  CHAPTER  ON  TINNING  GRAY  IRON  CASTINGS 


BY 

W.   T.    KLANDKRS 


PUBLISHED   BY  DAVID  WILLIAMS  COMPANY 

232-238  WILLIAM  ST.,  NEW  YORK 
1900 


COPYRIGHTED  1900 
BY  DAVID  WILLIAMS  COMPANY 


In  1876  the  firm  I  was  employed  by,  finding  it  neces- 
sary to  galvanize  the  goods  they  were  manufacturing, 
placed  the  matter  in  my  hands.  Having  little  or  no 
knowledge  of  the  process,  I  spent  considerable  money  in 
buying  technical  books  that  purported  to  treat  on  the 
subject,  but  found  that  what  little  they  had  to  say  was  of 
no  practical  value  whatever.  I  think  the  same  condi- 
tions prevail  now.  Since  1889  I  have  made  the  installa- 
tion of  galvanizing  and  tinning  plants  a  business  and  have 
built  nearly  sixty.  The  increased  demand  for  galvanized 
and  tinned  goods  within  the  last  ten  years  has  brought 
me  many  requests  from  people  for  information  regard- 
ing the  two  processes,  and  some  four  years  ago  I  gave  a. 
brief  description  of  the  process  of  galvanizing  in  THE 
IRON  AGE  and  THE  METAL  WORKER.  At  the  request  of 
the  publishers  I  have  undertaken  to  describe  the  different 
methods  of  coating  with  zinc  and  tin  by  immersion. 
Having  no  previous  work  on  the  subject  as  a  guide  and 
being  wholly  unused  to  writing,  I  realize  that  my  work 
lacks  the  finish  of  most  technical  books.  I  think,  however> 
that  my  treatment  of  the  several  subjects,  coupled  with  the 
illustrations  given,  will  enable  one  to  make  a  successful 
start  in  any  of  the  processes. 

W.  T.  FLANDERS. 

NASHUA.  N.  H. 


82923 


CONTENTS. 

Page, 

Galvanizing 7 

Locating  a  Plant  and  Selecting  a  Kettle 8 

The  Galvanizing  Room 8 

Tanks  for  Acids  and  Other  Purposes 10 

Tools  for  Galvanizing n 

Filling  and  Firing  a  New  Kettle 13, 

The  Use  of  a  Pyrometer: 13, 

Materials  Used  in  Galvanizing 14 

Building  and  Setting  Kettles 15 

Removing  Scale  with  Sulphuric  Acid 23 

Cleaning  Sandy  Castings  with  Sulphuric  Acid ....  24 
Preparing  the  Work  for  Dipping  in  the  Zincing 

Bath 25 

Drying  the  Work 25 

The  Heat  of  Zinc 27 

Dipping  the  Work  in  the  Molten  Metal 29 

The  Formation  of  Dross  in  the  Kettle 36 

Running  Over,  or  "  Sweating,"  Zinc  Dross 39 

Tinning  Malleable  Iron,  Wrought  Iron  and  Steel  43 

Preparing  the  Work 44 

Tools  and  Kettles 45 

A  Tinning  Plant 46 

Plan  of  Tinning  Plant 48 

Removing  Scale  and  Rust  with  Sulphuric  Acid ....  50 


Page. 

Cleaning  Sandy  Castings  by  Sulphuric  Acid 52 

Cleaning  Sandy  Castings  with  Hydrofluoric  Acid.  .  52 

Removing  Paint  or  Grease 53 

Tinning  with  a  Single  Kettle  of  Tin 54 

Tinning  with  Two  or  More  Kettles  of  Tin 55 

Passing  the  Work  Through  the  Tinning  Kettles .  .  56 

Tinning  Wire  in  Coils 58 

Tinning  Steel  Spoons  and  Similar  Articles 59 

Retinning 60 

Setting  Retinning  Kettles 64 

TINNING  COMMON  GRAY  IRON 66 

Description  of  Tinning  Plant 67 

General  Considerations 69 

Tumbling  Barrel 70 

Freeing  Gray  Iron  Castings  from  Sand  by  Hydro- 
fluoric Acid 74 

Cleaning  Sandy  Castings  with  Sulphuric  Acid ....  77 

The  Use  of  a  Hot  Alkali  Bath  in  Certain  Cases 78 

Preparing  the  Castings  in  the  Gas  Barrel 78 

Coating  the  Castings  with  Tin 83 


GALVANIZING. 


The  coating  of  articles  of  iron  and  steel  with  zinc,  or, 

as  the  process  is  generally  known,  "  galvanizing  "  them, 
as  a  means  of  retarding  oxidation  and  for  other  reasons, 
has  become  a  vast  industry,  in  which  a  large  number  of 
men  find  employment. 

It  is  not  our  purpose  to  attempt  a  description  of  the 
methods  employed  by  the  great  manufacturers  of  gal- 
vanized sheets  and  wire,  but  to  confine  our  efforts  to  the 
requirements  of  those  who  wish  to  engage  in  the  business 
in  a  small  way  and  to  enable  those  whose  location  would 
otherwise  compel  them  to  ship  goods  long  distances  to 
erect  and  operate  a  plant  of  their  own. 

It  may  not  be  out  of  place  to  say  that  it  has  been  the 
practice  of  some  engaged  in  the  business  to  make  as 
much  of  a  mystery  of  it  as  possible.  One  fallacy  given 
out  and  generally  credited  is  that  a  galvanizing  kettle 
must  not  be  allowed  to  cool  off.  This,  perhaps,  has  de- 
terred a  greater  number  from  attempting  their  own  work 
than  anything  else.  While  it  is  true  that  it  is  not  prac- 
ticable to  allow  a  kettle  holding  several  tons  of  metal  to 
cool  off  every  few  days,  there  is  no  reason  why  a  kettle 
containing  a  few  hundred  pounds  of  metal  cannot  be  al- 
lowed to  cool  when  it  is  not  required  for  use. 

While  it  is  our  purpose  to  treat  the  subject  in  a  way 
that  will  give  a  general  idea  of  the  whole  business,  our 
efforts  will  be  mostly  confined  to  explaining  the  methods. 

r 


8  GALVANIZING    AND   TINNING. 

to  be  employed  in  galvanizing  castings  of  gray  and  mal- 
leable iron,  small  articles  of  wrought  iron  and  steel  and 
sheet  metal  goods. 

LOCATING  A   PLANT  AND  SELECTING  A  KETTLE. 

To  those  contemplating  the  installation  of  a  galvaniz- 
ing plant  the  first  question  that  naturally  comes  up  is, 
where  can  it  best  be  located?  In  settling  this  question  it 
should  be  kept  in  mind  that  the  fumes  of  the  chemicals 
used  in  the  business  are  destructive  to  tools  and  machin- 
ery. For  this  reason  the  galvanizing  plant  should  be  in  a 
building  by  itself. 

The  next  question  is,  what  size  kettle  should  be  used 
and  what  is  the  best  material  to  make  it  of  ?  On  account 
of  the  difficulty  in  controlling  the  heat  of  a  small  body  of 
metal,  we  would  not  advise  the  use  of  a  kettle,  for  any 
purpose,  less  than  3  feet  in  length,  20  inches  in  depth  and 
1 8  inches  in  width.  The  material  for  the  kettle  should  be 
refined  iron  or  best  fire  box  steel,  and  should  not  be  less 
than  l/2  inch  thick. 

THE  GALVANIZING  ROOM. 

In  providing  a  room  or  a  building  in  which  to  locate 
the  plant,  provision  should  be  made  to  obtain  good  ven- 
tilation. It  should  be  high  posted  and  have  a  good  ventila- 
tor in  the  roof,  and  if  the  character  of  the  work  to  be 
done  will  admit,  a  hood  may  be  built  over  the  kettle,  com- 
ing low  enough  to  catch  all  the  smoke  possible,  while  not 
interfering  with  the  movements  of  the  operator.  When 
the  work  is  castings  or  small  articles,  there  is  no  objection 
to  having  the  hood  come  to  within  6  feet  of  the  floor,  and 
it  should  be  at  least  2  feet  larger  than  the  brick  work  sur- 
rounding the  kettle. 


GALVANIZING. 


Considerable  water  is  used  in  the  process,  and  provi- 
sion should  be  made  to  secure  proper  drainage.     A  good 


M 


Fig.  1.— Floor  Plan  of  Galvanizing  Room. 


plan  is  to  put  in  a  cement  floor,  which  can  be  laid  so  as  to 
provide  gutters  on  each  side  of  the  room.     If  the  work  to 


10  GALVANIZING    AND    TINNING. 

be  handled  is  castings  it  is  not  absolutely  necessary  to 
use  steam,  but  if  the  work  is  of  a  nature  that  requires  the 
removal  of  scale,  steam  should  be  brought  into  the  room. 
A  floor  space  25  x  50  feet  will  accommodate  such  an 
outfit  as  we  illustrate  by  Fig.  i.  A  much  less  floor  space 
can  be  made  to  accommodate  a  very  small  plant.  Fig.  i  is 
the  ground  plan  of  a  galvanizing  plant,  in  which  A  is  a 
tank  for  containing  a  solution  of  sulphuric  acid  and  water 
for  removing  scale  and  rust.  B  is  a  water  tank  for  stor- 
ing work  that  has  been  cleaned.  C  is  a  platform  where 
castings  are  placed  to  free  them  from  sand.  D  is  a  tank 
used  to  contain  the  solution  for  removing  the  sand  from 
the  castings  after  they  have  been  placed  on  the  platform. 
E  is  a  tank  for  muriatic  acid.  F  is  the  plate  for  drying 
the  work  before  immersing  it  in  the  molten  metal.  G  is 
the  kettle  containing  the  metal  and  H  is  the  tank  used  for 
cooling  the  work  after  it  is  coated  with  the  zinc.  I  I  in- 
dicate the  loose  planks  covering  the  ash  pits,  shown  in 
Fig.  3  as  M  M.  K  is  an  underground  flue  connecting  the 
drying  plate  F  with  a  chimney  or  stack,  L,  and  M  is  a  pit 
to  give  access  to  the  ash  pit  under  the  plate  F. 

TANKS  FOR  ACIDS  AND  OTHER  PURPOSES. 

The  illustration,  Fig.  i,  shows  wooden  tanks,  to  be 
built  as  shown  in  Fig.  12.  When  this  style  of  tank  is  em- 
ployed the  bolts,  in  those  designed  for  acid,  should  be  of 
copper.  Pine  or  cypress  makes  good  material  for  tanks. 
It  is  by  no  means  necessary  to  build  expensive  tanks  if 
the  work  to  be  done  is  small  articles.  If  oil  barrels  are 
sawed  in  half  and  thoroughly  cleaned  they  answer  every 
purpose,  provided,  of  course,  that  the  work  is  of  a  size 
that  half  barrels  will  accommodate. 

It  used  to  be  considered  necessary  to  line  acid  tanks 


GALVANIZING. 


II 


with  lead.  The  experience  of  the  writer  is  that  it  is 
money  thrown  away.  The  practice  has  been  almost  en- 
tirely abandoned. 


TOOLS   FOR  GALVANIZING. 


The  tools  employed  in  galvanizing  usually  consist  of 
tongs  of  various  shapes  and  sizes,  baskets  of  sheet  iron  or 
heavy  wire  cloth,  and  wires  bent  in  various  shapes.  The 
necessary  shape  of  the  tongs  will  be  suggested  by  the 


Fig.  2.— Top  View  of  Large  Galvanizing  Kettle. 

shape  of  the  article  to  be  handled.  In  Fig.  13  we  illus- 
trate the  shape  of  baskets  and  wires  most  generally  in 
use.  B  is  a  sheet  iron  basket  having  a  handle  about  3^2 
feet  long.  The  basket  should  be  about  8  inches  in  diam- 
eter at  the  top  and  7  inches  at  the  bottom,  with  a  depth  of 
9  inches.  Both  the  bottom  and  body  should  be  well  per- 
forated to  allow  the  metal  to  pass  out.  This  style  of 
basket  is  well  adapted  to  galvanizing  nails  and  other  small 
articles,  and  the  holes  should  be  of  a  size  that  will  not  ad- 


12 


GALVANIZING    AND    TINNING. 


mit  of  the  articles  being  handled  falling  through.  A  is 
a  basket  made  of  heavy  wire  cloth,  the  body  being  about 
8  inches  wide,  10  inches  long  and  6  inches  deep.  This 
basket  is  adapted  to  large  work  that  cannot  be  strung  on 
wires  and  is  too  small  to  be  handled  singly  with  tongs. 


Fig.  3.— Section  of  Fig.  2  at  A1,  A1. 


c  c 

Fig.  4. — Side  Elevation  of  Large  Galvanizing  Kettle 


E  and  G  are  wires  for  handling  small  \vork  in  the  molten 
metal.  F  is  a  scoop  for  removing  the  dross  from  the  bot- 
tom of  the  kettle.  D  and  H  are  skimmers,  and  E  is  a  hook 
to  suspend  in  the  molten  metal  articles  that  are  strung  on 
wires.  The  use  of  all  will  be  explained  in  their  turn 


GALVANIZING.  13 

Most  of  these  tools  are  adapted  to  use  in  tinning  as  well 
as  galvanizing. 

FILLING  AND  FIRING  A   NEW   KETTLE. 

In  filling  a  kettle  for  the  first  time  with  the  pigs  of 
zinc,  or,  as  it  is  termed  in  the  trade,  "  spelter/'  place  the 
metal  in  a  way  that  it  will  lie  as  closely  as  possible  to  the 
sides  of  the  kettle,  and  also  arrange  it  so  that  as  the 
outside  slabs  of  metal  melt  those  next  to  them  will  be 
forced  against  the  sides  of  the  kettle.  Unless  this  is  done 
the  kettle  is  apt  to  be  injured  by  the  heat.  Do  not  allow 
the  fires  to  burn  too  freely  in  melting  a  kettle  of  zinc  or 
in  firing  up  a  kettle  that  is  full  of  cold  metal.  In  melting 
a  kettle  of  metal  for  the  first  time  keep  the  fires  about  even 
with  the  molten  metal  in  the  kettle,  allowing  them  to  rise 
in  about  the  same  proportion  as  the  metal  melts.  Do  not 
use  the  top  drafts  until  the  molten  metal  is  about  even 
with  them. 

THE  USE  OF  A  PYROMETER. 

A  good  pyrometer  placed  in  the  kettle  will  be  found 
of  great  value  in  keeping  the  bath  at  a  uniform  temper- 
ature. Unless,  however,  the  stem  of  the  pyrometer  is 
protected  from  the  action  of  the  metal  it  will  soon  be  de- 
stroyed. The  writer  has  devised  a  means  by  which  the 
stem  of  the  pyrometer  is  kept  from  contact  with  the 
molten  zinc  and  at  the  same  time  gives  the  same  result  as 
though  the  molten  zinc  was  in  direct  contact  with  the 
pyrometer  stem. 

The  arrangement  consists  of  a  piece  of  2-inch  pipe 
about  20  inches  long,  with  one  end  closed  tight.  The  top 
of  the  pipe  is  provided  with  a  bushing,  with  a  hole  a  little 
larger  than  the  stem  of  the  pyrometer.  A  second  bushing 
should  also  be  placed  in  the  pipe  about  3  inches  from  the 


GALVANIZING  AND   TINNLNG- 


bottom.  These  bushings  serve  to  keep  the  pyrometer  in 
an  upright  position.  The  casing  surrounding  the  stercr"'* 
the  pyrometer  is  filled  with  lead,  so  that  when  the  arrange 
ment  is  placed  in  the  kettle  there  is  a  direct  metal  connec- 
tion with  the  stem  of  the  pyrometer.  Fig.  14  shows  a  py- 
rometer in  position  in  the  kettle,  while  Fig.  15  shows  the 
"  protector  "  in  detail. 

MATERIALS  USED  IN  GALVANIZING. 

The  principal  materials  used  in  galvanizing  are  zinc, 


Fig.  5.— Section  at  Grate  Line  of  Large  Galvanizing  Kettle. 

sal  ammoniac,  muriatic,  sulphuric  and  hydrofluoric  acids 
and  gas  coke.  We  cannot  with  fairness  express  a  prefer- 
ence for  any  brand  of  spelter,  and  will  only  say,  use  spel- 
ter smelted  by  a  reliable  firm,  keeping  in  mind  that  much  T" 
the  so-called  spelter  is  recovered  from  zinc  dross  by  pa*v 
iies  who  do  not  have  the  facilities  for  doing  the  work 
properly.  The  best  sal  ammoniac  to  use  is  the  "  gray 
granulated,"  although  the  "  white  granulated  "  answers 
every  purpose. 


GALVANIZING.  15 

BUILDING   AND   SETTING    KETTLES. 

In  deciding  what  size  kettle  to  put  in  you  must  be 
guided  by  the  nature  of  the  work  to  be  done.  If  it  is 
small  articles  that  are  to  be  handled,  and  the  amount  such 


0 

o 

i    D 


Fig.  6.—  Casting  Details  of  Large  Galvanizing  Kettle. 

as  will  only  require  the  plant  to  be  operated  at  intervals, 
a  kettle  3  feet  long,  18  inches  wide  and  20  inches  deep 
will  answer  the  purpose.  A  kettle  more  than  20  inches 
deep  makes  it  necessary  to  provide  ash  pits  at  the  sides, 
as  shown  in  Fig.  3  and  designated  M 


OF   THE 

UNIVERSITY 


16 


GALVANIZING   AND   TINNING. 


In  Figs.  7,  8  and  9  we  show  method  of  setting  a  small 
kettle  that  is  not  designed  to  be  operated  continually.  The 
grates  C  C  in  Fig.  9  are  bars  of  iron  that  may  be  with- 
drawn when  it  is  desired  to  let  the  fire  out  and  replaced 
when  required  for  use. 

Figs.  2,  3,  4  and  5  show  manner  of  setting  kettles  5  feet 
long  and  upward,  and  Fig.  6  gives  the  casting  details. 
Fig.  10  gives  shape  and  construction  of  kettle.  The  rivet- 


Fig.  7.— Top  Plan  of  Small  Galvanizing  Kettle. 

ing  in  the  heads  may  be  spaced  2J/>  inches,  while  the 
rivets  securing  the  stiffening  bars  to  the  sides  may  be 
spaced  4  inches.  For  kettles  from  4  to  6  feet  in  length 
material  %  inch  thick  will  answer  for  the  body  and  l/2 
inch  for  the  heads.  Above  6  feet  material  at  least  I  inch 
thick  should  be  used. 

Fig.  10  shows  a  kettle  in  which  the  body  is  formed  of 
one  piece,  and  with  the  rivets  where  the  fire  will  not  affect 
them.  A  kettle  for  general  use  built  after  this  illustration 


GALVANIZING. 


is  our  preference  for  many  reasons,  but  it  does  not  follow 

that  the  work  could  not.be  done  in  a  kettle  of  any  shape. 

A,  Fig.  6,  are  the  coping  plates,  the  position  of  which 

is  shown  in  Figs.  2,  3  and  4.    These  plates,  when  held  in 


ig.  8. -Section  of  Fig.  7  at  A',  A'. 


C  C 

Fig.  9.— Section  of  Small  Galvanizing  Kettle,  Showing  Method 
of  Setting  Grates. 

place  by  the  bolts  C,  serve  to  prevent  the  sides  of  the 
kettle  from  springing  outward  when  the  iron  blocks  D  D 
are  in  place,  as  shown  in  Figs.  2  and  3.  Coping  plates 
for  kettles  from  4  to  6  feet  long  should  be  2^2  inches 


i8 


GALVANIZING   AND   TINNING. 


thick  and  10  inches  wide.  The  fire  spaces  E  E  in  Figs.  2 
and  3  should  not  be  more  than  7  inches  wide  and  the  same 
length  as  the  inside  of  the  kettle. 

D  in  Fig.  6  are  the  blocks  designated  in  Figs.  2  and  3 
as  D.  F  in  Fig.  6  are  the  iron  plates  i  inch  thick.  Their 
positions  are  designated  in  Figs.  2  and  3  as  F.  G  in  Fig. 
6  is  a  section  of  grate,  the  position  of  which  is  designated 
in  Figs.  3  and  5  as  G  G.  The  openings  of  this  grate 
should  be  about  I  inch  wide  and  the  grates  should  be  wide 


Fig.  10. — End  and  Side  Elevations  and  Top  View  of  Large 
Galvanizing  Kettle. 

enough  to  span  the  fire  spaces  E  E  in  Figs.  2  and  3  and 
rest  on  plates  H  H  and  the  pier  I,  on  which  the  kettle  B 
rests,  as  shown  in  Fig.  3.  The  plate  H  in  Fig.  6  may  also 
be  used  to  cover  the  fire  spaces  E  E,  Figs.  2  and  3.  The 
plates  should  be  about  ]/2  inch  thick  and  12  inches  wide; 
their  length  is  determined  by  the  length  of  the  kettle.  K 
in  Fig.  6  is  the  casing  for  the  upper  draft  holes  indicated 
as  K  K  in  Figs.  3  and  4.  The  casing  should  be  about  10 
inches  long,  with  the  opening  about  4x4  inches.  It 
should  be  arranged  to  close  with  a  slide,  as  shown  in  Fig. 


GALVANIZING.  1 9 

4.  L  in  Fig.  6  shows  the  casings  for  the  lower  set  of 
drafts,  the  openings  in  which  should  be  8  x  12  inches. 
Their  position  in  the  brick  work  is  designated  in  Figs.  3, 
4  and  5  as  L.  Fig.  2  is  a  top  plan  of  the  brick  work.  Fig. 
3  is  a  vertical  section  at  A'  A'  and  Fig.  4  is  a  side  ele- 
vation. 

The  ash  pits  M  M,  in  Fig.  3,  should  be  about  2  feet 
wide.  The  pits  are  covered  with  loose  planks,  so  that 
access  to  the  lower  drafts  may  be  had  for  the  purpose  of 


Fig.  11. — Casting  Details  of  Small  Galvanizing  Kettle. 

opening  or  closing  them,  and  also  for  the  purpose  of  re- 
moving the  ashes  from  the  spaces  N  N  under  the  grates 
G  G,  Fig.  3. 

Fig.  5  is  a  horizontal  section  of  the  brick  work  at  the 
grate  line  and  shows  the  grates  G  G  in  position,  and  also 
the  manner  of  laying  the  bricks  between  the  draft  casings 
L  L.  I  indicates  the  pier  on  which  the  kettle  rests.  It 
will  be  seen  that  the  brick  work  between  the  lower  draft 
casings  L  L  is  built  in  a  way  to  allow  all  the  access  possi- 
ble to  the  grates  G  G  from  the  ash  pits  M  M.  The  plates 


.20 


GALVANIZING    AND   TINNING. 


H  H  are  used  to  rest  the  outer  edge  of  the  grates  G  G  on, 
and  also  to  support  the  brick  walls  at  each  side  of  the 
kettle.  The  walls  on  each  side  of  the  kettle  should  have 
a  lining  of  fire  brick  commencing  at  the  grate  and  ex- 
tending upward  to  the  coping  plates  A  A,  Fig.  3. 

Figs.  7,  8  and  9  show  manner  of  setting  a  kettle  that 
is  not  deep  enough  to  require  ash  pits  at  the  sides.      For 


Fig.  IS.— Details  of  Acid  Tank, 

casings  for  the  upper  and  lower  drafts  make  the  patterns 
as  shown  in  Fig.  6  and  which  are  designated  K  and  L. 
Fig.  7  is  a  top  plan  of  the  brick  work  surrounding  the  ket- 
tle. Fig.  8  is  a  vertical  section. of  Fig.  7  at  A'  A',  and 
Fig.  9  is  a  horizontal  section  at  B'  B'. 

Fig.  6  shows  all  the  casting  details  necessary  to  set  a 
kettle  in  the  manner  shown  in  Figs.  2,  3,  4  and  5.  The 
bolt  C  that  sets  in  the  brick  work  vertically  is  provided 
at  one  end  with  a  foundation  washer,  B,  which  is  held  in 
place  by  the  key  E.  The  positions  of  the  other  castings 


GALVANIZING. 


21 


in  this  figure  are  all  shown  by  corresponding  letters  in 
Figs.  2,  3,  4  and  5. 

Fig.  1 1  gives  the  casting  details  necessary  to  set  a  ket- 
tle after  the  plan  shown  by  Figs.  7,  8  and  9.     A  is  a  plate 


Fig.  23 —Galvanizing  Tools. 

to  cover  the  top  of  the  brick  work  surrounding  the  kettle, 
and  its  position  is  designated  in  Fig.  7  as  A.  B  is  a  cast- 
ing used  in  connection  with  bolts  passing  through  the  ends 
to  bind  the  brick  work  together.  Its  position  is  desig- 
nated in  Fig.  8  as  B.  C  is  the  grate,  the  position  of  which 
is  shown  in  Fig.  9  at  C,  and  D,  Fig.  n,  are  the  castings 


22  GALVANIZING    AND   TINNING. 

for  supporting  each  end  of  the  grates  C,  the  position  of 
which  is  designated  in  Figs.  8  and  9  by  D. 

A  kettle  for  galvanizing  pipe  should  be  23  feet  long, 
3  feet  deep  and  2  feet  wide.  One  for  sheet  iron  ware,  if 
it  is  intended  to  include  washtubs  and  garbage  cans, 
should  be  6  feet  long,  3  feet  wide  and  4  feet  deep.  Coal 
hods  can  be  galvanized  in  a  kettle  of  the  size  shown  in 


Fig.  14. — Perspective  of  Galvanizing  Kettle,  Showing 
Position  of  Pyrometer. 

Fig.  2 — viz.,  6  feet  long,  3  feet  deep  and  18  inches  wide. 
A  kettle  designed  especially  for  galvanizing  wire  should 
be  1 1  feet  long,  2  feet  deep  and  2  feet  wide.  Wire  cloth 
and  poultry  netting  is  best  run  in  a  kettle  6  feet  long,  4 
feet  wide  and  2  feet  deep. 

In  bricking  in  a  kettle  use  care  to  protect  all  the  calked 
joints  from  the  fire  and  do  not  make  the  fire  spaces  too 
wide.  If  too  much  space  is  left  for  fire  the  heat  of  the 
metal  cannot  be  kept  under  control. 


GALVANIZING. 


REMOVING  SCALE   WITH    SULPHURIC   ACID. 

Nearly  all  articles  made  of  wrought  iron  or  steel  or  of 
sheet  metal  are  covered -with  more  or  less  heavy  scale, 
which  must  be  completely  removed  before  the  zinc  will 


Fig.  15.— Pyrometer  t(  Protector  "  in  Detail 

adhere.  To  accomplish  its  removal  make  a  pickle  of 
sulphuric  acid  and  water,  i  part  acid  to  20  of.  water,  and 
bring  the  solution  to  a  temperature  of  about  150  de- 
grees F. 

The  length  of  time  required  to  accomplish  the  work 


24  GALVANIZING   AND   TINNING. 

varies  with  the  thickness  of  the  scale.  In  many  cases  it 
is  necessary  to  remove  part  of  it  with  some  sharp  pointed 
tool.  When  the  material  has  been  burned  in  welding, 
and  where  the  scale  has  been  rolled  deeply  into  the  stock, 
it  is  necessary  to  use  a  tool  to  loosen  the  scale.  Stock 
having  an  uneven  coating  of  scale  should  be  cleaned  in  a 
weaker  solution  than  that  having  an  even  coating  or  than 
that  having  a  light  scale.  The  reason  is  that  that  part 
of  the  stock  which  is  first  made  clean  will  be  overpickled 
before  the  parts  having  the  heavier  scale  are  clean. 

When  the  work  seems  perfectly  clean  and  free  from 
scale  or  rust  it  should  be  put  into  a  tank  containing  water 
enough  to  cover  it  completely.  A,  in  Fig.  I,  designates 
the  tank  to  be  used  for  treating  the  material  to  remove 
the  scale,  and  B  in  the  same  illustration  denotes  the  stor- 
age tank. 

CLEANING  SANDY  CASTINGS  WITH  SULPHURIC  ACID. 

Castings  that  are  sandy  may  be  cleaned  .by  pouring 
over  them  a  solution  of  sulphuric  acid  and  water,  I  part 
acid  to  6  of  water.  Place  the  castings  on  the  platform 
C  in  Fig.  i  and  wet  them  with  the  solution  which  is  con- 
tained in  tank  D,  Fig.  I.  Continue  this  operation  until 
the  sand  will  wash  off  by  the  application  of  water.  The 
castings  should  be  wet  every  hour  or  so,  and  they  should 
be  cleaned  in  about  12  hours. 

Cast  iron  that  has  been  allowed  to  remain  in  the  pickle 
too  long  will  be  covered  with  a  gummy  or  greasy  sub- 
stance, and  will  not  properly  take  the  coating  of  zinc  un- 
less it  is  left  in  the  metal  a  long  time,  and  even  then  it  will 
not  be  nicely  coated,  but  will  be  rough  and  covered  with 
thick  patches  of  metal.  It  will  not  have  the  gloss  that  a 
properly  prepared  casting  will  have.  We  refer  to  this 


OF  TBS 

UNIVERSITY 


method  of  cleaning  sandy  castings  in  the  chapter  on  tin- 
ning, and  it  will  be  well  to  read  what  is  said  there  in  this 
connection,  as  the  rules  there  given  apply  to  galvanizing, 
as  well  as  what  is  said  regarding  dry  tumbling  as  an  aid 
in  cleaning  work  for  tinning. 

PREPARING    THE     WORK     FOR     DIPPING     IN     THE     ZINCING 

BATH. 

To  enable  the  zinc  to  take  to  the  work  quickly  and 
firmly  a  solution  of  muriatic  acid  and  water  is  used.  This 
not  only  serves  as  a  flux,  but  it  removes  any  rust  that  has 
formed  on  the  work  in  the  operation  of  inspecting  and 
removing  the  scale  or  sand  that  the  sulphuric  acid  pickle 
failed  to  remove.  If  the  work  has  been  thoroughly 
cleaned  by  dry  tumbling  the  use  of  sulphuric  acid  is  not 
necessary.  If  no  rust  has  formed  on  the  work  all  that  is 
necessary  is  to  immerse  it  for  two  or  three  minutes  in  this 
muriatic  solution.  If  rust  is  present  it  must  be  immersed 
long  enough  to  remove  it. 

Some  galvanizers  use  full  strength  acid  for  this  pre- 
paratory dip,  but  we  prefer  to  dilute  the  acid  about  one- 
half  and  to  add  i  pound  of  sal  ammoniac  to  a  gallon  of  the 
mixture.  Tank  E,  Fig.  i,  is  for  containing  this  mixture. 

DRYING    THE    WORK. 

From  tank  C,  Fig.  i,  or,  in  other  words,  from  the 
muriatic  acid,  the  work  is  taken  to  the  place  provided  for 
drying  it.  The  position  of  this  drying  arrangement  is 
designated  F  in  Fig.  i.  This  drying  arrangement  may 
be  the  plates  covering  the  fires  that  heat  the  kettle.  If 
the  work  to  be  handled  only  amounts  to  a  few  hundred 
pounds  per  day  it  can  be  dried  in  this  way.  If,  however, 
the  amount  of  work  necessitates  keeping  the  kettle  in  con- 


26 


GALVANIZING   AND    TINNING. 


stant  operation,  a  drying  arrangement  such  as  shown  in 
Figs.  1 6,  17  and  18  should  be  provided.  Sheets  and  pipe 
should  be  dried  in  an  oven. 


Fig.  16.— Perspective  View  of  Drier. 


t 

/ 

| 

\ 

< 

t 

V 

1 

J 

•^S^)^ 

•t 

Fig.  17 .—Horizontal  Section  of  Fig.  16  at  Orate  Line. 


Fig.  18.— Vertical  Section  of  Fig.  16. 

The  location  of  this  drying  arrangement  is  a  mere 
matter  of  choice.  In  Fig.  I  we  show  it  located  at  one 
end  of  the  kettle.  The  work  should  be  perfectly  dry,  but 
it  should  not  be  allowed  to  get  hot  enough  to  burn  the 


GALVANIZING  27 

acid.  When  properly  dried  the  muriatic  acid  should 
show  on  the  surface  of  the  work  in  the  form  of  a  white 
powder.  Work  that  has  been  prepared  for  dipping  and 
dried  should  not  be  allowed  to  get  cold,  and  if  more  has 
been  prepared  for  dipping  than  can  be  finished  it  should 
not  be  allowed  to  remain  on  the  drier  over  night,  but  re- 
turned to  the  water  tank.  It  should,  of  course,  be  re- 
dipped  in  the  muriatic  solution  and  dried  again  before 
putting  it  into  the  zincing  kettle. 

Figs.  16,  17  and  18  show  a  good  arrangement  for 
drying  the  work.  Fig.  16  is  a  perspective  view  of  the 
completed  work,  Fig.  17  is  a  horizontal  section  of  Fig.  16 
at  grate,  and  Fig.  18  is  a  vertical  section. 

THE    HEAT   OF   THE    ZINC. 

This  part  of  the  business  is  not  only  the  most  difficult 
to  describe,  but  it  is  the  most  difficult  to  learn,  for  the 
reason  that  different  kinds  of  work  require  that  differ- 
ent temperatures  be  maintained.  A  kettle  of  zinc  at  the 
proper  heat  for  wire  or  wire  cloth  would  be  much  too  hot 
for  galvanizing  castings  of  either  gray  or  malleable  iron, 
while  with  the  zinc  at  the  proper  heat  for  large  work  it 
would  be  impossible  to  coat  small 'work  properly,  even  if 
the  material  was  the  same.  Large  pieces  require  that  a 
low  heat  be  maintained  on  the  zincing  bath.  Small  work 
that  is  strung  on  wires  for  dipping  requires  a  higher  heat 
of  the  zincing  bath  than  heavy  pieces.  Work  that  is  gal- 
vanized in  baskets  requires  a  higher  heat  of  the  zincing 
bath  than  work  that  is  strung  on  wires  and  drawn  from 
the  coating  bath  without  the  aid  of  a  flux  on  the  surface 
of  the  molten  metal,  as  hereafter  described. 

We  shall  give  the  degrees  of  heat  that  a  pyrometer 
should  indicate  when  different  kinds  of  work  are  being 


28  GALVANIZING    AND    TINNING. 

done,  basing  the  rules  given  on  the  supposition  that  when 
the  metal  is  barely  melted — that  is,  at  a  temperature  that 
would  just  keep  it  in  a  liquid  state,  the  pyrometer  indicates 
750  degrees  of  heat.  We  shall  also  give  the  best  rules 
possible  for  determining  the  proper  temperature  by  the 
looks  of  the  metal  and  by  other  signs. 

Large  gray  iron  castings  require  that  the  metal  be  at 
the  lowest  temperature  possible  and  have  it  liquid.  At 
about  this  temperature  it  will  be  silver  white  in  color,  will 
burn  sal  ammoniac  slowly  when  thrown  on  its  surface,  and 
when  a  skimmer  is  passed  over  its  surface  the  oxide  will 
be  slow  in  appearing.  In  this  condition  the  pyrometer 
should  indicate  about  775  degrees  of  heat.  This  tem- 
perature is  also  suitable  for  galvanizing  very  thin  castings 
that  it  is  designed  to  "  spangle  "  or  to  have  a  crystallized 
appearance — for  example,  sinks  and  like  work. 

For  small  castings  that  are  to  be  drawn  through  the 
metal  without  using  a  flux  the  pyrometer  should  indicate 
about  840  degrees.  At  this  temperature  the  metal  should 
have  a  slightly  bluish  cast,  burn  sal  ammoniac  moderately 
quick  and  show  the  oxide  in  a  few  seconds  after  the 
skimmer  has  been  passed  over  its  surface.  This  tem- 
perature is  about  right 'for  galvanizing  wrought  iron  pipe ; 
the  cheaper  grades  of  sheet  iron  or  goods  made  from  it, 
such  as  coal  hods,  ash  cans  and  chamber  pails.  Heavy 
malleable  iron  castings  will  also  coat  nicely  at  this  heat. 

For  small  work,  such  as  nails  and,  in  fact,  almost  any 
work  that  is  done  in  baskets  or  strung  on  wires  and  drawn 
through  a  flux,  the  pyrometer  should  indicate  from  870 
to  890  degrees  of  heat.  The  metal  should  burn  sal 
ammoniac  quickly  and  oxidize  quickly.  It  will  be  quite 
blue  in  color.  This  temperature  is  about  right  for  sheet 
steel  and  articles  made  from  it,  as  well  as  steel  pipe. 


GALVANIZING.  2£ 

DIPPING  THE  WORK  IN  THE   MOLTEN   METAL. 

We  will  describe  the  manner  of  handling  several  dif- 
ferent articles  as  a  general  guide  for  handling  all  kinds 
of  work.  Considerable  skill  is  required  to  bring  a  piece 
of  work  out  of  the  metal  and  cool  it  so  that  the  surface 
will  be  smooth,  free  from  blisters  and  with  no  lumps  of 
surplus  metal  attached. 

Before  dipping  the  work,  cover  the  surface  of  a  part 
of  the  molten  zinc  with  a  flux  of  sal  ammoniac  to  keep  the 
oxidized  metal  from  adhering  to  it.  To  prepare  this  flux 
sprinkle  a  few  handfuls  of  sal  ammoniac  on  the  surface  of 
the  molten  metal,  and  as  soon  as  it  is  melted  add  a  few 
drops  of  glycerine.  This  will  cause  the  flux  to  thicken 
up  and  will  prevent  it,  in  a  measure,  from  covering  the 
entire  surface  of  the  metal.  The  glycerine  also  causes 
the  flux  to  remain  stationary,  so  that  when  the  operator  is 
ready  to  draw  the  article  from  the  bath  the  flux  will  not 
cover  the  space  he  has  cleared  with  his  skimmer  for  that 
purpose.  The  tool  designated  D  in  Fig.  13  is  used  for 
the  purpose  of  skimming  the  surface  of  the  metal  before 
drawing  the  work  from  the  bath. 

This  flux  not  only  prevents  the  zinc  from  oxidizing, 
but  it  assists  the  metal  to  take  quickly  and  evenly  to  the 
work.  Keep  the  flux  fresh  by  adding  more  sal  ammoniac 
from  time  to  time. 

We  will  suppose  the  article  to  be  dipped  is  a  cast  iron 
sink  or  some  similar  casting — that  is,  a  thin  casting. 
Have  the  metal  at  the  temperature  first  described  under 
tht  heading  "  The  Heat  of  the  Zinc."  After  satisfying- 
himself  that  the  casting  is  perfectly  dry  and  hot  enough  to 
have  expelled  all  moisture  from  it  the  operator  catches  the 
article  with  a  pair  of  tongs  and  plunges  it  as  quickly  as 
possible,  and  not  cause  the  metal  to  spatter,  into  the  mol- 


T  T  -VT  T  -r  -r  •»-»  *-, 


;3O  GALVANIZING  AND   TINNING. 

ten  zinc.  He  must  hold  the  article  beneath  the  zinc  until 
it  is  as  hot  as  the  zinc  itself.  After  the  article  has  been  in 
the  bath  a  few  minutes  it  should  be  rinsed  around  in  the 
metal  in  such  a  way  that  the  flux  floating  on  the  surface 
of  the  molten  zinc  will  come  in  contact  with  all  parts  of  it. 
When  the  article  is  thoroughly  coated  clear  a  space  on  the 
surface  of  the  molten  zinc  with  the  skimmer,  and  after 
{lusting  on  a  very  little  dry  powdered  sal  ammoniac  draw 
the  article  from  the  metal. 

In  performing  this  operation  catch  the  article  with 
the  tongs  in  such  a  way  that  the  part  they  grasp  will  be 
the  last  to  leave  the  metal.  Do  not  lift  the  article  clear 
cf  the  metal  with  the  tongs  you  use  in  the  metal,  but  pro- 
vide a  second  pair  to  handle  the  article  with  until  it  is 
cooled.  In  drawing  the  article  raise  it  slowly  with  the 
tongs  held  in  the  position  described,  and  as  soon  as  it  is 
partly  clear  of  the  metal  grasp  it  with  the  tongs  provided 
for  that  purpose,  and  complete  its  removal.  Hold  the 
article  in  such  a  position  as  will  admit  of  the  metal  flowing 
to  one  point,  and  just  as  the  drop  is  about  to  harden  re- 
move it  with  a  stiff  brush  or  an  old  file.  Expose  the  ar- 
ticle to  the  air  until  crystals  appear,  and  then  brush  it 
with  a  brush  wet  in  clear  water.  Do  not  dip  the  article 
in  water,  especially  if  it  is  a  sink  or  a  very  thin  casting,  as 
that  would  be  quite  likely  to  break  it.  In  any  event  the 
coating  would  not  be  as  bright  as  it  would  be  if  left  to  cool 
gradually  after  brushing  with  the  wet  brush.  Thick 
heavy  castings  may  be  dipped  in  water  at  once  on  remov- 
ing them  from  the  molten  metal. 

Coal  hods  and  similar  goods  of  sheet  steel  or  iron  only 
require  to  be  left  in  the  bath  a  few  seconds.  The  flux 
through  which  they  pass  should  be  confined  at  one  end  of 
the  kettle  by  a  piece  of  sheet  iron  long  enough  to  go  across 


GALVANIZING.  31 

the  kettle  from  side  to  side.  This  is  called  a  "  flux  guard," 
and  it  should  enter  the  metal  about  2  inches,  with  the 
upper  edge  as  high  or  a  little  higher  than  the  sides  of  the 
kettle.  In  galvanizing  sheet  metal  ware  the  flux  should 
be  made  to  foam  up  nearly  to  the  top  of  the  kettle  by  using 
glycerine.  The  goods  should  be  passed  through  this  flux 
into  the  metal,  and  as  soon  as  they  are  coated,  which  will 
be  in  a  very  few  seconds,  they  must  be  passed  under  the 
flux  guard  to  the  end  of  the  kettle  that  is  kept  free  of  flux. 
In  passing  the  article  under  the  flux  guard  keep  the  open- 
ing up  so  that  none  of  the  flux  will  be  carried  along  with 
it.  Remove  the  article  from  the  metal  in  the  way  just  de- 
scribed for  sinks  and  similar  articles,  but  do  not  sprinkle 
the  surface  of  the  zinc  with  sal  ammoniac.  Allow  the 
work  to  cool  in  the  air.  If  any  particles  of  the  sal  am- 
moniac have  adhered  to  the  work  in  drawing  it  from  the 
molten  metal  remove  them  with  a  wet  brush. 

Some  articles  can  be  galvanized  very  nicely  by  string- 
ing them  on  stout  wires  about  \y2  feet  long.  When  this 
method  is  employed  string  on  a  number  of  the  pieces,  and 
then  bring  both  ends  of  the  wire  together  and  clinch  them 
securely.  To  suspend  work  in  the  metal  strung  this  way 
use  a  hook,  shaped  after  the  form  given  in  Fig.  13  and 
designated  C.  Provide  several  of  these  hooks,  so  that  a 
batch  may  always  be  ready  when  the  previous  one  is  re- 
moved from  the  kettle.  A  piece  of  %-inch  round  iron, 
bent  in  the  shape  of  the  letter  S,  will  serve  to  remove  the 
strings  of  castings  from  the  hooks,  and  also  for  handling 
them  after  they  are  removed.  The  wires  E  and  G,  Fig.  13, 
are  intended  for  stringing  small  articles  on  for  the  pur- 
pose of  dipping  them  in  the  molten  metal. 

In  handling  small  articles  on  these  wires  use  a  motion, 
after  they  are  drawn  from  the  metal,  calculated  to  free 


32  GALVANIZING   AND   TINNING. 

them  of  surplus  metal  and  also  to  prevent  their  adhering 
to  each  other  when  they  are  plunged  in  the  water.  To  do 
this  properly  will  require  some  practice. 

It  is  a  good  plan  to  warm  the  cooling  water  slightly 
for  cooling  some  articles,  and  to  have  a  thin  film  of  oil  on 
the  surface.  Small  articles  strung  on  wires  may  be  drawn 
through  the  metal  after  sprinkling  on  a  small  quantity  of 
powdered  sal  ammoniac,  or  may  be  drawn  through  a  clear 
thin  flux  of  sal  ammoniac,  to  which  a  few  drops  of  glycer- 
ine have  been  added.  If  the  latter  plan  is  used,  as  it  should 
be  if  the  articles  are  such  as  are  liable  to  rub  and  stick 
together,  the  oil  should  not  be  used  on  the  cooling  water. 

Small  work  that  cannot  be  strung  on  wires  may  be 
galvanized  by  using  a  basket  of  wire  or  sheet  iron.  We 
have  already  described  these,  and  they  are  designated  in 
Fig.  13  as  A  and  B. 

When  these  baskets  are  employed  the  flux  should  be 
of  a  consistency  that  will  run  freely  among  the  work.  A 
block  of  iron  should  be  placed  in  a  position  beside  the 
kettle  that  will  permit  the  operator  to  rest  the  handle  of 
his  basket  over  the  block  with  the  basket  hanging  over 
the  kettle.  Using  this  block  as  a  rest,  the  operator  should 
shake  the  basket  sharply,  and  for  several  seconds,  to  free 
the  work  of  surplus  metal,  and  when  it  is  accomplished 
he  will  shake  them  into  the  water  to  cool  them,  after  which 
dry  them  off  by  dipping  them  in  boiling  water  and  then 
throwing  them  into  sawdust.  Nails  or  tacks  may  be 
shaken  out  of  the  basket  onto  an  iron  plate,  placed  at  an 
angle,  over  a  tub  of  water.  The  plate  should  be  inclined 
sufficient  to  allow  the  work  to  slide  into  the  water  readily. 

Sheet  iron,  wire,  wire  cloth  and  poultry  netting  are 
mostly  passed  through  the  zincing  bath  mechanically,  and 
as  the  means  employed  are  too  expensive  and  complicated 


GALVANIZING.  33 

to  illustrate  or  describe  we  shall  not  attempt  it.  Sheet 
iron  may  be,  and  once  was,  galvanized  by  parting  the  ket- 
tle lengthwise  with  a  flux  guard.  The  side  where  the 
prepared  sheet  enters  the  bath  is  covered  with  a  sal  am- 
moniac flux,  and  the  opposite  side,  where  it  leaves  the  bath, 
is  covered  with  coke  dust  to  the  depth  of  about  I  inch. 
A  light  single  block  and  fall  is  used  to  assist  in  drawing 
the  sheet  from  the  kettle,  and  every  kettle  in  which  work 
of  large  size  is  galvanized  should  be  so  provided. 

Wire  cloth,  wire  and  poultry  netting  may  be  galva- 
nized by  running  it  through  the  kettle  by  means  of  a  reel. 
In  galvanizing  wire  cloth  and  poultry  netting  the  kettle 
should  be  parted  by  a  flux  guard,  as  previously  described, 
and  the  coke  dust  piled  up  to  a  depth  of  several  inches  and 
kept  sprinkled  with  water  by  using  an  ordinary  watering 
pot.  The  flux  should  be  present  where  the  work  enters 
the  metal. 

Wire  requires  no  flux  at  the  point  where  the  work 
enters  or  on  any  other  part  of  the  kettle.  Sand  or  coke 
dust  or  dies  of  asbestos  may  be  used  to  wipe  off  the  sur- 
plus metal.  If  the  kettle  for  wire  is  the  usual  length  of 
10  feet  the  wire  may  be  drawn  through  the  metal  at  a 
speed  of  about  75  feet  per  minute.  If  it  is  being  done  in 
a  short  kettle  the  speed  must  be  slow  enough  to  allow  the 
work  to  be  perfectly  coated. 

In-  Fig.  19  we  give  the  position  of  the  different  pieces 
of  apparatus  required  to  do  the  work  in  a  small  way. 
Large  plants  equipped  to  do  this  work  exclusively  are 
fitted  with  reels  driven  by  power,  and  several  strands  are 
run  through  simultaneously.  In  Fig.  19  A  is  the  position 
of  the  reel  holding  the  black  wire,  B  is  the  tank  holding 
the  muriatic  acid,  C  is  the  kettle,  D  a  tank  containing 
water  and  E  the  position  of  the  reel  for  drawing  the  wire. 


34 


GALVANIZING   AND    TINNING. 


CD 


i 


GALVANIZING. 


35 


Fig.  SO.— Perspective  of  Dross  Kettle. 


Fig.  21.— Top  Plan  of  Dross  Kettle. 


GALVANIZING    AND    TINNING. 


THE  FORMATION  OF  DROSS  IN  THE  KETTLE. 

The  waste  caused  by  the  formation  of  dross  is  quite 
large,  even  with  an  experienced  man  in  charge  of  the  ket- 


Fig.  22.— Vertical  Section  of  Fig.  21  at  A.  A. 


Fig.  S3.— Horizontal  Section  of  Fig.  22  at  Orate  Line. 

tie.  The  amount  of  dross  made  is  increased  by  failure  in 
keeping  the  metal  at  a  temperature  that  will  not  injure  it, 
by  allowing  the  work  to  be  lost  in  the  kettle  and  through 


GALVANIZING. 


37 


Fig.  24.— Details  of  Dross  Kettle. 


38  GALVANIZING   AND    TINNING. 

immersing  in  the  kettle  work  that  has  not  been  properly 
prepared. 

As  the  dross  forms  it  settles  at  the  bottom  of  the  kettle, 
and  when  the  accumulation  is  such  that  it  interferes  with 
the  work  it  must  be  removed.  As  the  dross  settles  it  be- 
comes hard,  and  is  easily  removed  by  the  proper  appliance 
for  that  purpose.  The  tool  for  removing  the  dross  is 
called  a  "  dross  scoop."  In  Fig.  13  we  show  the  shape 
of  this  tool,  designated  F,  where  a  round  bottom  kettle  is 
in  use.  The  handle  of  the  scoop  should  be  about  twice 
the  length  of  the  kettle,  unless  the  kettle  is  of  a  size  that 
requires  the  use  of  tackle  in  dressing  it.  The  scoop 
should  be  well  perforated  to  allow  the  clear  metal  to  flow 
back  into  the  kettle.  In  removing  the  dross  use  care  not 
to  stir  or  rile  more  than  possible  when  forcing  the  dross 
scoop  into  the  hardened  mass.  Force  the  scoop  into  the 
dross  gently,  and  when  you  are  satisfied  that  the  scoop 
is  full,  raise  it  out  of  the  metal  by  resting  the  handle  of 
the  scoop  on  the  end  of  the  kettle  to  get  a  leverage.  Let 
the  scoop  remain  over  the  kettle  until  all  the  clear  metal 
that  will  has  dripped  back  into  it.  If  the  handle  of  the 
scoop  is  rapped  with  a  hammer  or  piece  of  iron  it  will 
cause  more  of  the  clear  metal  to  separate  from  the  dross 
than  would  be  the  case  if  it  was  not  done.  As  soon  as 
the  clear  metal  has  ceased  to  drip  dump  the  dross  into  cast 
iron  pans.  These  pans  should  be  about  2  inches  deep,  15 
inches  long  and  9  inches  wide. 

Dross  hardens  very  rapidly  when  exposed  to  the  air, 
and  no  more  time  than  is  necessary  to  allow  all  the  metal 
possible  to  drip  back  into  the  kettle  should  be  consumed 
in  getting  it  into  the  dross  pans. 

If  there  is  a  large  amount  of  dross  in  the  kettle  and  it 
is  desired  to  allow  the  ikes  to  go  completely  out  it  should 


GALVANIZING.  39 

be  removed.  If  the  kettle  is  allowed  to  cool  with  a  large 
amount  of  dross  lying  in  the  bottom  of  it  the  result  will 
most  likely  be  a  burst  kettle.  Before  commencing  to 
dross  the  kettle — that  is,  remove  the  dross — skim  all  the 
flux  from  the  surface  of  the  metal  with  a  perforated 
skimmer.  This  tool  is  shown  in  Fig.  13,  and  is  desig- 
nated H. 

RUNNING  OVER  OR  "  SWEATING  "  ZINC  DROSS. 

The  writer  is  often  asked  if  it  pays  the  galvanizer  to 
try  and  recover  the  good  metal  from  the  dross,  and  how 
best  to  accomplish  it.  Without  entering  into  a  discussion 
regarding  the  desirability  of  attempting  its  recovery,  from 
a  financial  point  of  view,  we  will  say  that  it  is  our  prac- 
tice to  "  sweat  "  our  dross. 

In  Fig.  20  we  give  a  perspective  view  of  the  kettle 
and  brick  work  for  running  over  dross.  Fig.  21  is  a  top 
view,  Fig.  22  is  a  vertical  section  at  A  A  and  Fig.  23  is 
a  horizontal  section  at  the  grates.  The  kettle  and  casting 
details  for  bricking  in  are  shown  in  Fig.  24.  The  ar- 
rangement is  so  simple  that  we  do  not  think  it  necessary 
to  describe  it  in  detail. 

The  kettle  should  be  made  of  cast  iron,  with  the  bot- 
tom about  i  inch  thick.  A  kettle  30  inches  in  diameter 
and  20  inches  deep  answers  the  purpose  very  well. 

To  separate  the  good  metal  from  the  dross  first  melt 
up  about  6  or  8  inches  of  lead  in  the  bottom  of  the  kettle 
and  then  put  in  the  dross.  Bring  the  dross  to  a  temper- 
ature that  will  cause  it  to  have  rather  a  dark  blue  color 
or  where  the  pyrometer  will  register  about  1050  degrees. 
When  this  is  accomplished  stir  the  mass  with  a  long- 
handled  ladle  for  about  one-half  hour,  and  then  allow  it  to 
settle.  When  the  mass  has  settled  the  lead  will  be  at  the 


40  GALVANIZING   AND   TINNING. 

bottom,  the  dross  will  lie  on  the  lead  and  the  clear  metal 
will  be  at  the  top,  where  it  can  be  bailed  out  into  pans. 
The  stirring  may  be  repeated  once  or  twice  after  each 
bailing  operation.  After  all  the  clear  metal  has  been  ex- 
tracted that  can  be  remove  the  dross  and  put  it  into  pans. 


TINNING  IRON  AND  STEEL 


TINNING  MALLEABLE  IRON, 

WROUGHT  IRON  AND  STEEL 

Simply  to  give  articles  of  malleable  and  wrought  iron 
a  coating  of  tin  is  a  comparatively  easy  process  to  master, 
but  tinning  on  certain  articles  of  hardware  has  reached  a 
high  state  of  perfection,  and  to  tin  saddlery  hardware  and 
the  cheaper  grades  of  table  cutlery  requires  considerable 
skill.  The  methods  employed  to  do  the  work  vary  greatly 
in  different  establishments,  and  the  degree  of  perfection 
attained  is  equally  at  variance.  Work  that  is  tinned  in  an 
indifferent  and  slovenly  manner  is  not  necessarily  done 
cheaply,  as  the  material  wasted  on  an  article  roughly  and 
imperfectly  coated  is  of  more  value  than  the  slight  saving 
in  labor  cost  obtained  by  rushing  the  work  through  without 
proper  attention  to  obtaining  a  light  and  even  coating. 
The  high  price  of  the  metal  used  to  tin  articles  makes 
the  cost  of  the  material  much  more  than  the  labor  cost.  A 
loss  of  10  per  cent,  of  the  material  by  careless  handling 
would  represent  a  much  larger  proportion  of  the  entire 
cost  of  the  work  than  would  an  increase  of  the  same  per 
cent,  added  to  the  labor  cost.  Painstaking  in  bringing 
out  the  finished  article  free  from  surplus  tin  not  only 
adds  greatly  to  the  commercial  appearance  of  the  goods, 
but  materially  decreases  the  cost  of  the  work.  This  eco- 
nomical result  is  reached  by  careful  attention  to  the  heat 
of  the  tinning  bath  and  to  the  skillful  handling  of  the 
articles  after  their  removal  from  the  tinning  pot  and  be- 

43 


44  GALVANIZING   AND    TINNING. 

fore  they  are  cooled.  If  the  tin  is  not  hot  enough  the 
articles  will  be  heavily  coated,  and  it  will  cool  on  the  work 
bunchy  and  wavy.  A  degree  of  heat  above  a  certain 
limit  also  causes  the  work  to  have  a  rough  and  uneven 
appearance,  injures  the  color  and  destroys  the  luster. 
The  use  of  a  good  pyrometer  in  a  tinning  bath  is  a  great 
help  to  the  operator  in  maintaining  a  uniform  heat  of  the 
tin. 

PREPARING   THE    WORK. 

Ordinarily  the  common  grades  of  tinned  articles  are 
made  ready  for  tinning  by  simply  removing  the  sand,  scale 
or  rust  by  an  application  of  either  commercial  sulphuric, 
muriatic  or  hydrofluoric  acid.  The  finer  grades  of  work 
are  prepared  for  tinning  by  careful  and  lengthy  rolling 
in  gravel  and  water.  This  preparation  not  only  effect- 
ually removes  all  impediments  to  a  perfect  coating,  but 
gives  the  articles  a  smooth  and  perfect  surface  on  which 
to  deposit  the  tin,  the  degree  of  perfection  obtained  being 
determined  by  the  time  and  care  expended  in  the  rolling 
operation. 

A  piece  of  wrought  iron  from  which  the  scale  has  been 
removed  by  the  application  of  acid  will  not  have  the 
smooth  and  perfect  coating  that  the  same  would  have  if 
the  removal  of  the  scale  was  accomplished  by  irritation. 
The  same  is  true  of  articles  of  malleable  iron.  The  best 
and  most  perfect  results  are  obtained  by  giving  the  cast- 
ings a  thorough  tumbling  in  gravel  and  water,  which 
operation  brings  the  surface  of  the  castings  to  a  state  of 
smoothness  only  equaled  by  burring  or  grinding.  Mal- 
leable castings  on  which  it  is  desired  to  obtain  a  fine  fin- 
ish should  invariably  be  given  this  treatment.  It  is,  of 
course,  necessary  that  the  patterns  from  which  castings 


TINNING.  45 

are  taken  that  are  designed  to  be  tinned  be  made  with  a 
view  to  obtaining  the  smoothest  surface  possible  as  an 
assistance  to  the  tumbling  operation. 

Some  tinners  not  only  roll  their  castings  in  gravel  and 
water,  but  for  the  purpose  of  obtaining  a  still  finer  surface 
than  can  be  obtained  by  this  method  they  roll  them  in 
dry,  coarse  sand,  and  also  give  them  a  third  rolling  with 
scraps  of  leather,  the  entire  operation  often  requiring  30 
or  40  hours  in  going  through  the  several  treatments. 
Water  rolling  is  so  common  and  so  thoroughly  understood 
that  we  consider  it  unnecessary  to  go  into  detailed  instruc- 
tions regarding  the  apparatus  to  be  used  or  the  methods 
to  be  employed.  There  are  several  concerns  who  make 
the  manufacture  of  rolling  barrels  for  this  purpose  a  spe- 
cialty, and  the  cheapest  method  to  adopt  in  equipping  a 
tinning  plant  with  wet  rolling  barrels  would  be  to  buy  the 
outfit  from  a  manufacturer  who  has  made  the  business  a 
study. 

The  care  of  the  tin,  in  regard  to  keeping  it  free  from 
dross  or  slag,  is  an  important  point  in  obtaining  perfect 
work,  and  will  be  referred  to  in  its  proper  place, 

TOOLS  AND  KETTLES. 

The  tools  employed  in  handling  the  work  are  very 
simple  in  construction.  They  consist  of  wires  formed 
into  various  shapes,  perforated  •  ladles  or  baskets  made 
from  sheet  iron  or  wire  cloth,  and  tongs  with  the  jaws 
formed  to  adapt  themselves  to  the  various  articles  it  is 
designed  to  handle  with  them.  Those  illustrated  by  Fig. 
13  in  chapter  on  galvanizing  will  be  found  useful  and  all 
that  will  be  required  in  many  cases.  The  ingenuity  of 
the  operator  will  readily  suggest  what  is  required  for  the 
work  in  hand. 


46  GALVANIZING   AND   TINNING. 

The  number  of  tinning  kettles  to  be  used  depends  alto- 
gether on  the  class  of  goods  to  be  tinned.  The  most  com- 
mon kinds  of  hardware  specialties  can  be  tinned  very  sat- 
isfactorily by  the  use  of  a  single  kettle  of  tin,  while  the 
better  class  of  tinning,  such  as  saddlery  hardware,  iron 
spoons,  etc.,  require,  in  order  to  get  the  best  results,  two 
kettles,  and  three  may  be  employed  to  good  advantage. 

Where  a  plant  is  fitted  up  to  do  a  fine  grade  of  tinning 
the  kettle  used  to  give  the  castings  their  first  coating  of 
tin  is  designated  as  the  "  roughing  kettle."  and  the  other 
kettle  or  kettles  as  the  finishing.  When  the  roughing  ket- 
tle is  used  no  particular  care  is  necessary  to  have  the  ar- 
ticles come  out  smoothly  coated  or  free  from  surplus  tin, 
as  the  unevenness  of  the  coating  will  be  removed  by  their 
later  treatment  in  finishing.  The  object  of  the  roughing 
kettle  is  to  give  the  iron  a  thorough  coating  of  tin  as 
rapidly  as  it  is  prepared  to  receive  it,  which  prevents  rust- 
ing. After  the  iron  receives  a  thorough  coating  of  tin  it 
may  be  stored  away  until  it  is  desired  to  finish  it. 

For  those  having  only  a  small  amount  of  tinning  to 
do  it  would  not  pay  to  invest  in  an  expensive  outfit  of  wet 
rolling  barrels,  and  very  good  results  can  be  obtained 
without  them.  We  will  say  here  that  only  a  few  of  the 
large  concerns  engaged  in  tinning  are  so  fitted  and  the 
work  they  turn  out  is  of  a  nature  that  calls  for  the  best 
results  possible  to  obtain  as  regards  smoothness  and 
brightness  of  the  finished  work. 

A  TINNING  PLANT. 

In  installing  a  tinning  plant  the  convenient  handling 
of  the  work  should  be  given  all  the  consideration  possible, 
and  the  operator  will  find  it  a  great  help  toward  making 
his  work  easy,  as  well  as  to  the  advantage  of  his  employer, 


TINNING.  47 

if  he  will  make  a  study  of  the  best  methods  and  tools  to 
employ  in  handling  the  various  articles  that  come  to  him 
to  be  tinned. 

While  it  is  our  purpose  to  treat  this  subject  in  a  man- 
ner that  will  enable  a  novice  to  make  a  successful  begin- 
ning, the  best  results  can,  of  course,  only  be  reached  by 
actual  practice.  With  the  principles  and  requisites  nec- 
essary to  perfection  in  results  obtained  well  understood, 
there  should  be  no  trouble  experienced  by  one  of  average 
mechanical  ability  in  mastering  the  business. 

To  make  the  different  operations  of  preparing  and  tin- 
ning articles  of  malleable  iron,  wrought  iron  and  steel 
easily  understood,  we  shall  treat  each  operation  separately. 

While  the  illustrations  we  give  will  serve  as  a  general 
guide  in  equipping  a  plant,  it  does  not  follow  that  they 
must  not  or  cannot  be  changed  to  suit  local  conditions. 
It  would  be  impossible  to  illustrate  the  exact  course  to  be 
followed  in  individual  cases,  and  those  undertaking  the  in- 
stallation of  a  plant  must  be  governed  to  a  great  extent 
by  their  requirements  as  they  see  them. 

It  should  be  kept  in  mind  in  deciding  what  part  of  the 
factory  can  best  be  devoted  to  the  tinning  department 
that  more  or  less  gases  and  fumes  prevail  when  the  work 
is  carried  on.  These  gases  and  fumes  are  not  only  dis- 
agreeable to  inhale,  but  are  destructive  to  fine  machinery 
and  tools  and  to  finished  work.  To  the  end  that  the  work 
may  not  become  a  source  of  annoyance  to  those  not  im- 
mediately engaged  in  it  and  detrimental  to  machinery  and 
goods,  the  plant  should  be  located  if  possible  in  a  build- 
ing by  itself,  taking  good  care  to  provide  good  ventilation 
and  drainage. 

A  room  devoted  to  this  work  should  not  be  less  than 
10  feet  in  hight,  and  the  kettles  and  acid  tanks  provided 


48  GALVANIZING   AND   TINNING. 

with  hoods  connected  with  the  ventilators  to  carry  off  the 
gases.  The  hoods  should,  of  course,  be  high  enough  not 
to  interfere  with  the  perfectly  free  movements  of  the 
operator. 

The  illustrations  given  contemplate  tanks  of  cypress 
or  pine  for  containing  the  different  solutions  used,  in  pre- 
paring and  finishing  the  work,  but  oil  barrels  sawed  in 
half  may  be  employed  for  the  purpose  if  they  are  properly 
cleaned  either  by  burning  out  the  interior  or  washing  in 
a  hot,  strong  solution  of  soda  ash  and  water. 

For  heating  the  tin  hard  coal  is  best,  as  it  gives  the 
most  even  heat  and  is  most  easily  controlled.  Soft  coal, 
coke,  natural  gas  and  even  wood  can,  however,  be  em- 
ployed for  the  purpose. 

PLAN   OF  TINNING  PLANT. 

We  show  in  Fig.  25  a  ground  plan  for  a  tinning 
plant  for  general  work,  except  the  tinning  of  common 
cast  iron.  In  this  illustration  A  denotes  the  roughing 
kettle — that  is.  the  kettle  containing  the  tin  used  to  give 
the  work  its  first  coating  of  tin ;  B  is  the  finishing  kettle ; 
C  is  the  tank  containing  muriate  of  zinc ;  D  is  what  is 
termed  in  the  trade  the  "  whipping  box,"  which  is  simply 
an  arrangement  to  prevent  the  drops  of  molten  tin  being 
thrown  promiscuously  over  the  room  when  the  operator 
is  shaking  or  swinging  his  work  to  free  it  from  the  sur- 
plus metal ;  E  is  a  tank  made  of  sheet  iron  for  containing 
the  kerosene  oil  used  in  cooling  the  work,  the  intent  being 
to  have  this  tank  surrounded  by  running  water  to  keep 
the  oil  cool,  the  water  being  contained  in  the  companion 
tank  F ;  G  is  a  tank  provided  with  a  steam  coil,  the  intent 
being  to  have  the  tank  filled  with  clean  hot  water,  in  which 
to  rinse  the  finished  work  before  drying  it  off  in  the  saw- 


TINNING. 


49. 


50  GALVANIZING   AND   TINNING. 

dust,  which  is  contained  in  the  box  H ;  I  and  O  are  water 
tanks  used  for  storing  the  work  after  it  has  been  treated 
in  the  acid ;  K  is  a  tank  containing  muriatic  or  sulphuric 
acid ;  L  and  M  are  acid  tanks,  the  use  of  which  will  be 
explained  in  the  proper  place ;  N  is  a  tank  for  containing 
an  alkali  solution,  and  it  should  be  provided  with  a  steam 
coil ;  R  R  denotes  a  drain  through  the  center  of  the  room 
to  carry  off  the  waste  water.  A  sectional  plan  of  this 
floor  is  given  in  Fig.  38. 

REMOVING  SCALE  AND  RUST  WITH  SULPHURIC  ACID. 

To  enable  steel  and  wrought  iron  to  take  a  coating  of 
tin,  the  scale  and  rust  must  be  removed.  This  is  best  ac- 
complished with  a  pickle  composed  of  I  part  sulphuric 
acid  to  about  30  to  40  of  water,  bringing  the  solution  to  a 
temperature  of  about  150  degree  F. 

If  the  articles  are  of  such  a  shape  that  they  pack 
closely  together  they  must  be  stirred  so  that  the  acid  will 
have  free  action  on  all  parts  alike,  otherwise  the  scale  or 
rust  will  not  be  affected  on  that  part  that  is  in  contact  with 
another  piece,  the  result  being  that  the  acid  will  burn  the 
material  first  made  clean  before  the  scale  is  removed  from 
the  part  in  contact. 

In  pickling  sheets  they  must  be  placed  in  racks  that 
will  prevent  one  sheet  lying  against  another.  Sheets 
should  be  carefully  inspected,  and  any  spots  that  the  acid 
has  not  touched  must  be  removed  with  the  aid  of  a  sharp 
pointed  steel.  The  shank  of  an  old  file  ground  to  a  point 
and  hardened  answers  the  purpose  very  well. 

If  the  articles  are  small,  and  it  is  desired  to  give  them 
a  fine  surface,  roll  them  in  sand  and  water  after  remov- 
ing the  scale  and  rust  with  the  acid  solution,  and  to  fur- 
ther improve  their  surface  give  them  a  second  rolling  in 


TINNING.  51 

scraps  of  leather.  The  effect  of  rolling  is  to  give  the 
articles  a  smooth  surface,  and  the  smoother  the  surface 
obtained  the  smoother  and  brighter  will  be  the  goods  after 
tinning. 

We  do  not  wish  it  to  be  understood  that  the  rolling 
operation  is  absolutely  necessary  to  obtain  a  complete 
coating  of  the  goods,  as  they  will  take  the  tin  perfectly  if 
that  operation  is  omitted,  but  the  appearance  of  the  goods 
is  greatly  improved  by  the  rolling,  and  when  it  is  desired 
to  obtain  the  best  finish  possible  the  rolling  barrel  must 
be  employed. 

When  the  removal  of  scale  and  rust  has  been  affected 
and  the  material  is  perfectly  clean  it  should  be  stored  in 
tanks  containing  clear  water,  there  to  remain  until  the 
operator  is  ready  to  put  it  through  the  subsequent  opera- 
tions. Do  not  allow  the  work  to  remain  in  running  water, 
as  it  will  soon  rust  or  oxidize  if  it  is. 

The  operator  must  not  fail  to  examine  the  work  fre- 
quently while  it  remains  in  the  hot  pickle  to  determine 
when  the  desired  result  has  been  obtained.  If  it  is  al- 
lowed to  remain  too  long  a  time  after  the  scale  and  rust 
have  been  removed  the  acid  will  attack  the  surface  of  the 
material  and  leave  it  rough  and  seamed.  Imperfections 
caused  by  overpickling  cannot  be  covered  up  by  the  coat- 
ing of  tin,  and  the  commercial  appearance  of  the  goods  is 
injured. 

The  removal  of  scale  and  rust  can  be  accomplished  by  a 
pickle  composed  of  I  part  muriatic  acid  to  15  to  20  parts 
of  water,  but  the  cost  is  greater  and  the  result  obtained  no 
better.  It  is  not  advisable  to  use  this  acid  for  the 
purpose  unless  the  amount  of  work  to  be  treated  is  very 
limited. 

In  Fig.  25  K  represents  the  tank  to  be  used  for  the 


52  GALVANIZING   AND    TINNING. 

purpose  just  explained,  and  I  indicates  the  storage  tank 
for  the  prepared  work. 

CLEANING  SANDY  CASTINGS  BY  SULPHURIC  ACID. 

Castings  that  have  sand  on  them  must  be  subjected  to 
a  treatment  that  will  effectually  remove  it,  as  a  perfect 
coating  cannot  be  obtained  if  a  particle  of  sand  remains. 
The  removal  of  sand  can  be  accomplished  by  placing  the 
castings  on  an  inclined  platform  and  keeping  them  wet 
with  a  pickle  composed  of  i  part  sulphuric  acid  to  6  of 
water,  until  the  sand  is  loosened  enough  to  wash  off  by 
the  application  of  water.  From  10  to  20  hours  is  re- 
quired to  accomplish  its  removal  and  then  a  casting  brush 
often  has  to  be  employed  to  get  out  all  the  little  particles 
that  are  burned  in  where  there  are  sharp  angles. 

Rolling  with  plenty  of  sharp  scratches  or  shot  is  the 
only  sure  way  to  obtain  a  perfectly  clean  casting,  and  we 
should  never  attempt  to  tin  malleable  castings  in  any  con- 
siderable quantity  without  the  aid  of  a  rolling  barrel.  As 
in  the  case  with  articles  of  steel  or  wrought  iron,  the  wet 
rolling  barrel  supplemented  by  the  dry  rolling  in  leather 
scraps  fits  the  castings  to  take  a  beautiful  coating  of  tin 
and  a  bright  luster. 

The  platform  on  which  the  castings  are  placed  for 
pickling  should  have  a  tank  placed  under  one  end  at  its 
lowest  point  to  catch  the  acid  as  it  flows  from  the  castings 
after  each  bailing  operation.  This  pickling  arrangement 
is  designated  as  L  in  Fig.  25,  and  the  tank  designated  as 
M  can  be  used  to  store  the  prepared  work  until  it  is  de- 
sired to  give  it  the  finishing  treatments. 

CLEANING    SANDY    CASTINGS    WITH     HYDROFLUORIC    ACID. 

We  have  given  the  course  to  be  followed  for  cleaning 
sandy  castings  with  sulphuric  acid,  because  it  may  not  al- 


TINNING.  53 

ways  be  possible  to  obtain  hydrofluoric  acid,  and  because 
hydrofluoric  acid  is  a  comparatively  new  agent  in  the 
business.  Where  it  is  possible  to  substitute  this  powerful 
acid  for  sulphuric  acid  it  should  be  employed,  as  its  effects 
are  much  more  rapid  and  certain,  and  are  less  destructive 
to  the  castings. 

In  employing  hydrofluoric  acid  to  remove  sand  make 
a  solution  for  slow  pickling  in  the  proportion  of  I  part 
acid  to  30  of  water.  For  quick  pickling  make  the  pro- 
portion i  of  acid  to  20  of  water.  Immerse  the  castings 
until  the  sand  is  dissolved,  which  will  be  in  from  15  min- 
utes to  3  hours,  depending  on  the  strength  of  the  solu- 
tion and  the  tenaciousness  of  the  sand. 

A  good  arrangement  for  doing  this  work  is  to  have 
two  tanks,  one  elevated  by  means  of  a  bench  or  stand,  so 
that  the  bottom  of  the  upper  tank  will  be  a  few  inches 
above  the  top  of  the  lower  tank.  Provide  a  hole  in  the 
upper  tank  so  that  when  the  plug  is  removed  the  solu- 
tion will  escape  into  the  lower  tank  and  leave  the  castings 
uncovered  by  the  solution.  When  all  the  solution  has  'es- 
caped into  the  lower  tank  cover  the  castings  with  water 
until  it  is  desired  to  remove  them  for  subsequent  treat- 
ments. The  solution  in  the  lower  tank  is  ready  to  use  on 
a  fresh  batch  of  castings.  We  do  not  show  this  arrange- 
ment in  Fig.  25,  as  it  can  take  the  place  of  the  sulphuric 
acid,  designated  as  M  in  that  illustration. 

REMOVING    PAINT    OR    GREASE. 

If  the  work  is  greasy  or  has  paint  on  it,  it  must  be 
cleaned  with  a  hot  solution  of  caustic  soda  or  soda  ash 
and  water.  Make  the  solution  very  hot  and  strong,  and 
immerse  the  work  in  it  until  it  is  free  from  all  such  mat- 
ter, after  which  rinse  it  thoroughly  in  clean  water.  This 


54  GALVANIZING   AND   TINNING. 

operation  should  precede  pickling  when  it  is  necessary  to 
perform  it.  The  tanks  for  this  purpose  are  designated  in 
Fig.  25  as  N  and  O. 

TINNING  WITH   A  SINGLE   KETTLE  OF  TIN. 

As  already  stated,  very  good  results  can  be  obtained  by 
simply  using  one  kettle  of  tin  where  the  commercial  ap- 
pearance of  the  work  is  of  secondary  importance.  Where 
only  a  single  kettle  is  employed  the  tin  should  be  main- 
tained at  a  temperature  of  about  500  degrees  F.,  and  the 
work  may  be  cooled  in  hot  water  and  dried  off  in  saw- 
dust. 

The  operations  preliminary  to  dipping  the  work  in  the 
tinning  bath  are  precisely  what  they  would  be  if  more 
than  one  kettle  of  tin  was  used.  As  these  operations  will 
be  explained  in  connection  with  those  for  using  two  ket- 
tles we  will  not  give  them  here. 

Where  only  a  single  kettle  is  employed  more  or  less 
trouble  will  be  experienced  in  keeping  the  dross  or  slag 
which  rises  to  the  surface  of  the  tin  from  adhering  to  the 
work  and  in  keeping  the  tin  at  a  uniform  temperature. 
The  dross  or  slag  must  be  removed  from  the  tin  fre- 
quently with  a  perforated  skimmer,  and  when  the  black 
flux  that  forms  on  the  surface  of  the  tin  from  the  muriate 
of  zinc,  in  which  the  castings  are  dipped  previous  to  im- 
mersing them  in  the  molten  tin,  is  present  in  sufficient 
quantities  to  interfere  with  drawing  the  work,  it  must 
also  be  removed  in  part.  A  small  amount  is  beneficial  to 
the  work,  but  when  it  accumulates  in  a  sufficient  quantity 
to  catch  on  the  work  as  it  is  drawn  out  it  is  apt  to  stain 
the  work  and  leave  white  streaks  wherever  it  touches. 
The  cooling  water  should  also  be  kept  clean  and  free  from 
acid.  If  it  is  not  the  work  is  liable  to  rust.  In  Figs.  29, 


TINNING.  55 

30  and  31  we  show  manner  of  bricking  in  a  single  kettle, 
the  casting  details  being  shown  in  Fig.  32. 

TINNING  WITH  TWO  OR  MORE  KETTLES  OF  TIN. 

When  the  work  has  been  made  perfectly  clean  from 
sand,  scale,  rust,  grease  or  paint  by  some  one  of  the  treat- 
ments described,  it  is  ready  for  the  final  operations.  If 
the  work  is  of  a  kind  that  will  admit  of  its  being  strung  on 
wires,  use  such  wires  as  seem  best  adapted  to  the  work 
in  hand.  For  many  kinds  of  work  a  piece  of  wire  bent  in 
the  shape  of  a  croquet  wicket  will  be  found  just  the  thing. 
Good  stiff  wires  should  be  used,  and  they  should  be  long 
enough  to  allow  plenty  of  room  for  the  operator  to  grasp 
the  ends  without  getting  burned.  That  is  to  say,  if  you 
have  10  inches  of  tin  in  the  kettle,  make  the  wire  20  inches 
long,  which  will  allow  10  inches  of  wire  to  be  out  of  the 
tin  where  the  operator  can  grasp  it  when  he  is  ready  to 
draw  the  work  from  the  kettle.  Provide  plenty  of  these 
wires  so  that  the  handling  of  the  work  may  be  facilitated. 

String  on  wires  as  much  of  the  work  as  you  think  you 
can  handle  comfortably,  and  put  them,  several  strings  at  a 
time,  into  the  alkali  solution.  The  work  may  be  allowed 
to  remain  in  this  solution  for  several  minutes,  or  while  the 
operator  is  filling  more  wires.  From  the  alkali  solution 
the  work  is  to  be  passed  into  the  rinsing  tank,  and  care 
should  be  taken  that  all  traces  of  the  alkali  are  removed. 

When  this  is  accomplished  the  work  is  to  be  given  a 
few  minutes'  immersion  in  a  solution  of  muriatic  acid  and 
water.  This  mixture  should  be  in  the  proportion  of  I 
of  acid  to  4  or  5  of  water  in  cold  weather,  while  in  warm 
weather  8  or  10  of  water  to  i  of  acid  will  do  the  required 
work.  The  object  of  this  dip  is  to  remove  any  trace  of 
rust  that  may  have  formed  on  the  work.  The  tank  for 


56  GALVANIZING    AND    TINNING. 

this  purpose  is  designated  as  K  in  Fig.  25,  and  for  many 
kinds  of  work,  such  as  castings  that  have  been  cleaned  by 
dry  rolling  and  goods  that  have  been  made  of  material  that 
has  no  scale  on  it,  all  that  is  necessary  is  to  give  it  a  few 
minutes'  immersion  in  this  solution. 

From  this  last  dip  of  muriatic  acid  and  water,  which 
by  the  way  should  never  be  omitted,  the  work  is  to  be 
dipped  in  muriate  of  zinc,  which  is  the  last  dip  previous  to 
immersing  it  in  the  molten  tin.  Tank  C,  Fig.  25,  is 
used  to  contain  the  muriate  of  zinc,  which  solution  is  made 
by  dissolving  scraps  of  zinc  in  clear  muriatic  acid. 

PASSING  THE  WORK  THROUGH  THE  TINNING  KETTLES. 

If  two  kettles  of  tin  are  in  use,  as  shown  in  Fig.  25  by 
A  and  B,  take  a  wire  full  of  the  work  to  be  dipped  and  im- 
merse it  while  wet  with  the  muriate  of  zinc  in  the  kettle 
of  tin  designed  to  give  the  work  its  first  coating.  This  is 
the  roughing  kettle,  and  is  designated  in  Fig.  25  as  A. 
Put  several  of  the  strings  of  work  into  the  kettle  and 
allow  them  to  remain  until  the  work  is  as  hot  as  the  tin. 
The  tin  in  this  kettle  should  be  maintained  at  a  heat  of 
about  500  degrees  F. 

After  the  work  has  remained  in  the  first  kettle  the 
requisite  time  take  a  wire  full  in  the  left  hand,  and  with 
a  skimmer  held  in  the  right  hand  clear  a  space  on  the  sur- 
face of  the  tin  large  enough  to  admit  of  the  wire  full  of 
work  being  removed  without  any  of  the  slag  or  flux  ad- 
hering to  it.  Remove  the  wire  full  of  work  and  pass  it 
directly  to  the  second  kettle.  It  is  not  necessary  to  shake 
off  the  surplus  tin  when  removing  from  the  first  kettle, 
but  it  is  necessary  to  use  care  that  none  of  the  flux  or  slag- 
is  carried  over  to  the  second  kettle  on  the  work. 

Retaining  hold  of  the  wire  containing  the  work  the 


TINNING.  57 

operator  allows  it  to  remain  in  the  second  kettle  for  the 
fraction  of  a  minute  until  the  heat  of  the  work  attained  in 
the  first  kettle  is  reduced  to  about  the  temperature  of  the 
tin  in  the  second  kettle,  which  for  most  purposes  should  be 
about  400  degrees  F.  Very  small  articles  may  require  that 
the  tin  in  the  second  kettle  attain  a  temperature  of  450 
degrees  F.  A  much  higher  heat  will  cause  the  tallow, 
which  is  on  the  second  kettle,  to  a  depth  of  ^  to  I  inch,  to 
ignite.  When  the  work  is  in  the  condition  named  draw 
it  quickly  from  the  tin,  and  after  a  few  rapid  swinging 
motions  to  free  it  of  surplus  metal  plunge  it  into  a  tank 
of  kerosene  oil,  using  a  motion  calculated  to  keep  the  ar- 
ticles from  sticking  together.  A  little  practice  will  soon 
determine  what  motion  is  best  adapted  to  keep  the  ar- 
ticles separated  and  also  prevent  any  lumps  of  tin  form- 
ing on  the  work. 

D  in  Fig.  25  denotes  the  position  of  the  box  provided 
to  catch  the  drops  of  tin  that  are  thrown  from  the  work 
as  the  operator  swings  it  to  and  fro.  E  denotes  the  tank 
for  containing  the  oil  used  for  cooling,  as  already  ex- 
plained. The  tank  containing  this  oil  should  be  sur- 
rounded by  water  to  prevent  the  oil  heating  to  a  point 
where  it  would  ignite. 

The  work  should  be  allowed  to  remain  in  the  oil  long 
enough  to  set  the  tin,  and  it  should  then  be  thrown  into 
fine  sawdust  to  clean  it  of  the  oil.  If  the  articles  are  very 
heavy  it  may  be  necessary  to  plunge  them  into  cold  water 
from  the  oil. 

If  the  work  cannot  be  strung  on  wires  a  "  basket  "  may 
be  used  for  dipping  it.  The  basket  may  be  of  sheet  iron, 
in  which  case  it  should  be  provided  with  plenty  of  holes 
to  allow  the  tin  to  pass  off,  or  it  may  be  made  of  wire  net- 
ting with  a  mesh  sufficiently  small  to  prevent  the  work 


58  GALVANIZING   AND   TINNING. 

falling  through.  Fig.  13  illustrates  the  shape  of  these 
baskets,  which  are  designated  as  A  and  B.  Nails,  tacks, 
rivets  and  all  similar  articles  are  dipped  in  the  tin  by 
means  of  these  baskets.  Tongs  are  also  used  for  handling 
heavy  articles,  but  those  used  in  the  tin  should  not  be  used 
for  cooling  the  work,  as  they  would  mark  it.  The  tongs 
used  for  cooling  should  not  be  put  into  the  molten  tin. 
Their  shape  may  be  varied  to  suit  the  form  of  the  article 
handled. 

TINNING    WIRE    IN    COILS. 

In  large  manufacturing  establishments  machinery  is 
employed  whereby  several  strands  of  wire  are  passed 
through  the  tinning  kettle  simultaneously.  To  do  the 
work  on  a  small  scale,  provide  reels  that  will  accommo- 
date a  coil  of  wire.  Place  one  of  the  reels  in  a  position 
where  the  black  wire  will  pass,  as  it  is  uncoiled,  through 
a  tank  containing  muriate  of  zinc,  and  then  through  the 
kettle  of  tin.  The  other  reel  is  placed  in  a  position  where 
it  will  take  up  the  wire  as  it  passes  through  the  tin.  The 
reel  used  to  draw  the  work  through  the  kettle  must,  of 
course,  be  provided  with  an  arrangement  for  turning  it, 
and  a  device  to  hold  the  wire  under  the  muriate  of  zinc 
and  also  under  the  tin  as  it  passes  from  one  reel  to  the 
other  must  be  employed.  As  the  necessary  arrangement 
will  readily  suggest  itself  we  do  not  think  it  necessary  to 
illustrate  it. 

At  the  point  where  the  wire  leaves  the  molten  tin  a 
piece  of  tow  is  twisted  around  the  strand,  sufficiently 
tight  to  wipe  off  the  surplus  metal,  which  flows  back  into 
the  kettle.  If  the  wire  is  very  heavy  it  must  be  made  to 
pass  through  water  after  it  leaves  the  tin,  the  water  tank 
being  placed  where  the  wire  will  not  enter  it  until  it  has 


TINNING.  59 

passed  through  the  bunch  of  tow  used  to  wipe  off  the 
surplus  metal. 

If  the  wire  is  covered  with  a  heavy  scale  or  rust  it 
must  be  cleaned  in  sulphuric  acid  the  same  as  any  other 
work.  If  it  is  bright  wire  all  that  is  necessary  is  to  im- 
merse it  in  a  solution  of  muriatic  acid  and  water,  i  part 
acid  to  6  of  water.  If  wire  is  to  be  tinned  in  quantity  a 
long  shallow  kettle  is  best  adapted  to  the  purpose. 

TINNING  STEEL  SPOONS  AND  SIMILAR  ARTICLES. 

For  this  purpose  provide  a  good  sized  kettle  for 
"  roughing  "  the  work — that  is,  for  giving  it  a  prepar- 
atory coating.  For  finishing  the  work  use  small  kettles. 
A  kettle  15  inches  long,  8  inches  wide  and  6  inches  deep 
is  ample  for  work  of  this  kind.  We  refer  to  a  plant  fitted 
especially  for  this  business.  The  work  can  be  done  in  an 
outfit  such  as  we  illustrate  by  Fig.  25,  but  large  finishing 
kettles  are  not  as  well  adapted  for  this  business  as  small 
ones,  as  the  tin  in  a  large  kettle  is  apt  to  become  dull  in 
color  by  constant  use,  while  in  a  small  kettle  the  tin  is 
turned  over  more  rapidly,  which  allows  it  to  hold  its  color 
much  better. 

The  articles  should  be  rolled  in  tumbling  barrels 
with  scraps  of  leather  and  then  carefully  cleaned  in 
an  alkali  solution.  After  rinsing  off  the  alkali  they  should 
be  immersed  in  quite  a  strong  solution  of  muriatic  acid 
and  water  for  five  or  ten  minutes,  and  then  dipped  in  the 
roughing  kettle  by  means  of  a  wire  basket,  first  dipping 
the  work  in  a  solution  of  muriate  of  zinc.  As  soon  as' 
they  are  thoroughly  coated  shake  them  out  of  the  basket 
in  such  a  way  as  will  insure  the  separation  of  as  many  as 
possible.  It  makes  no  difference  whether  they  come 


60  GALVANIZING   AND   TINNING. 

smooth  or  not  so  long  as  they  are  thoroughly  coated. 
The  smoothness  will  come  in  the  finishing  operation. 

To  finish  the  goods  take  them,  a  piece  at  a  time,  in  a 
pair  of  tongs  adapted  to  hold  them  and  immerse  in  the 
finishing  kettle,  the  tin  in  which  is  covered  with  beef  tal- 
low to  the  depth  of  about  ^  inch.  As  soon  as  the  article 
reaches  the  same  heat  as  the  tin  remove  it  and  allow  it  to 
cool  enough  so  that  the  tin  will  not  run,  after  which  wipe 
up  the  goods  in  flour. 

RETINNING. 

This  branch  of  the  business  is  comparatively  simple, 
since  no  pickling  is  required.  An  outfit  for  doing  the 
work  usually  consists  of  the  three  kettles — one  for  rough- 
ing the  work  and  two  for  finishing.  The  roughing  ket- 
tle is  usually  set  up  by  itself,  although  it  may  be  con- 
tained in  the  same  brick  work  with  the  finishing  kettles. 

For  redlining,  kettles  shaped  like  those  used  for  sweat- 
ing zinc  dross  are  best  adapted  for  the  work,  and  the  man- 
ner of  setting  is  practically  the  same.  They  should  be 
covered  with  a  hood  to  catch  the  smoke  and  fumes  which 
are  constantly  rising.  The  hood  should  be  constructed 
to  leave  one  side  open  so  that  the  operator  has  free  access 
to  the  kettles  from  one  side.  A  view  of  a  "  tinning  stack  " 
resembles  an  open  grate  or  the  fire  place  of  olden  times, 
the  brick  setting  to  the  kettles  being  about  the  hight  of  an 
ordinary  work  bench. 

The  finishing  kettles  are  kept  covered  with  beef  tal- 
low and  palm  oil,  and  care  must  be  taken  to  prevent  any 
dross  or  slag  being  carried  over  from  one  kettle  to  the 
other  in  the  operation  of  passing  the  work  from  kettle  to 
kettle.  When  large  articles  are  being  treated,  like  pressed 


TINNING. 


6r 


dishpans,  a  swab  of  hemp  is  often  used  to  free  the  article 
from  dross  before  removing  it  to  the  last  kettle. 

In  drawing  the  article  from  the  finishing  kettle  the 


Fig.  26.— End  Elevation  of  Brick  Work  for  Setting  Two  Kettles* 


Fig.  27.— Vertical  Section  through  Fig.  26  at  A\  A\ 

motion  should  not  be  too  rapid.  The  piece  should  be  held 
in  one  position  and  the  drop  of  tin  that  forms  at  the  low- 
est point  removed  by  passing  a  piece  of  round  iron  along 


62 


GALVANIZING   AND    TINNING. 


the  edge.     One  end  of  this  rod  of  iron  is  kept  in  the  kettle 
of  tin  so  that  it  is  always  ready  for  use. 

When  the  tin  has  "  set,"  the  article  is  passed  to  the 


Fig.  28.— Horizontal  Section  through  Fig.  26  at  B\  B\ 


Fig.  29.— End  Elevation  of  Brick  Work  for  Setting  Single 
Kettle. 

"  bench  "  to  be  rubbed  in  flour.  In  large  establishments 
girls  are  mostly  employed  to  clean  the  work  with  flour 
after  it  is  tinned. 


TINNING.  63 

The  heat  of  the  tin  must  be  gauged  to  a  nicety.  If 
too  hot  the  tallow  will  ignite  and  the  work  come  out  yel- 
low. If  too  cool  the  coating  will  be  heavy  and  will  not 
flow  smoothly. 

It  is  perhaps  unnecessary  to  say  that  in  case  rust  has 


Fig.  SO.— Section  through  Fig.  29  at  A1,  A1 


Fig.  31.— Section  of  Fig.  29  at  B\  B\ 


formed  on  the  work  from  any  cause  it  must  be  removed 
with  acid  the  same  as  from  any  other  work.  Preparatory 
to  dipping  in  the  roughing  kettle  the  work  must  be  dipped 
in  muriate  of  zinc. 


GALVANIZING    AND    TINNING. 


SETTING  RETINNING  KETTLES. 

Kettles  for  redlining  are  set  in  a  variety  of  ways,  and 
hardly  any  two  plants  have  the  same  arrangement  of  kettles 
or  other  apparatus.  The  principal  point  to  consider  in 


1 


Fig.  82.— Details  of  Tinning  Kettle. 

bricking  in  kettles  for  retinning  and,  in  fact,  those  for  any 
purpose,  is  to  place  the  fire  and  ash  pit  doors  where  they 
will  not  interfere  with  the  working  of  the  kettles  while  the 
fires  are  being  attended  to. 


TINNING. 


We  give  in  Figs.  39  and  40  perspective  views  of  the 
brick  setting  of  a  redlining  stack.  Fig.  39  shows  the  ket- 
tles in  position,  and  Fig.  40  is  a  view  of  the  back  of  the 
stack,  showing  the  fire  and  ash  pit  openings. 

In  these  illustrations  the  entire  stack  is  represented  as 
being  of  brick.  This  plan  is  undoubtedly  the  most  eco- 
nomical in  the  end,  although  many  stacks  are  inclosed 
with  sheet  iron  about  the  brick  work  surrounding  the 
kettles.  We  think  the  perspective  views  will  enable  one 
to  construct  a  stack  without  our  giving  the  entire  arrange- 
ment in  detail,  as  we  do  in  Figs.  26  to  31,  inclusive. 

Fig.  32  shows  the  casting  details  for  setting  kettles  as 
represented  by  Figs.  26  to  31,  inclusive.  A  gives  a 
top,  side  and  end  view  of  the  kettle  ;  B  shows  the  coping 
plate  :  C  is  the  grate  in  detail  ;  D  is  the  front  bearing  bar 
in  detail,  and  E  the  back  bearing  bar.  The  position  of 
each  piece  is  designated  by  a  corresponding  letter  in  Figs. 
26  to  31,  inclusive. 

Fig.  26  is  an  end  elevation  of  the  brick  work,  Fig.  27 
is  a  vertical  section  of  Fig.  26  at  A'  A'  and  Fig.  28  is  a 
horizontal  section  of  Fig.  26  at  B'  B'.  Figs.  29,  30  and 
31  show  the  manner  of  bricking  in  a  single  kettle. 


TINNING  COMMON    GRAY   IRON. 

The  tinning  of  common  gray  iron  castings  has  become 
quite  an  extensive  industry  in  the  last  seven  or  eight  years. 
Previous  to  this  time  there  were  only  one  or  two  parties  in 
the  country  able  to  do  the  work  with  any  degree  of  suc- 
cess. While  manufacturers  had  long  recognized  the  fact 
that  tin  was  a  much  more  desirable  metal  than  zinc  for 
coating  certain  articles  of  culinary  use  the  want  of  a  cheap 
and  practical  process  for  tinning  on  gray  iron  precluded 
their  giving  the  matter  serious  attention. 

The  author  perfected  a  method  in  1891,  a  full  descrip- 
tion of  which  will  be  given  in  this  article,  that  proved  a 
practical  success,  and  to-day  it  is  almost  impossible  to  sell 
zinc  coated  articles  that  are  to  be  used  in  the  preparation 
of  food. 

In  addition  to  the  uses  to  which  tinned  gray  iron  is 
put  by  the  manufacturers  of  kitchen  and  other  hardware 
specialties,  it  has  been  found  of  great  advantage  to  give 
articles  of  cast  iron  that  are  to  be  copper  or  brass  plated  a 
coating  of  tin  previous  to  plating  them.  The  advantages 
come  from  the  lessened  quantity  of  material  necessary  to 
use  in  electroplating,  the  preventing  of  '"  leaking "  or 
"  sweating/''  so  common  where  the  plating  is  deposited 
directly  on  the  bare  casting,  and  also  in  giving  the  articles 
the  appearance  of  spelter  or  brass  castings. 

By  this  process  gray  iron  castings  are  prepared  for 
tinning  by  rolling  them  in  a  solution  of  muriatic  acid,  sal 
ammoniac  and  water,  the  rolling  barrel  being  constructed 


TINNING.  67 

to  retain  at  a  high  pressure  the  gas  formed  by  the  chem- 
icals used.  The  use  of  this  barrel  makes  it  desirable  to 
locate  the  tinning  plant  in  a  building  by  itself,  as  the  gas 
generated  is  constantly  escaping,  carrying  with  it  quan- 
tities of  the  solution.  At  the  best  the  barrel  room  for 
gray  iron  tinning  is  a  wet,  dirty  place,  and  the  entire  op- 
eration requires  the  use  of  considerable  water. 

DESCRIPTION  OF  TINNING  PLANT. 

In  erecting  a  building  for  this  purpose  particular  atten- 
tion should  be  paid  to  ventilation  and  drainage.  A  plan 
for  constructing  a  floor,  with  a  view  to  perfect  drainage, 
is  shown  by  Fig.  38.  The  arrangement  of  the  outfit  is 
shown  by  Fig.  33,  in  which  A  is  the  rolling  barrel  for  pre- 
paring the  castings  for  tinning.  B  is  a  tank  to  receive  the 
castings  after  they  have  been  treated  in  the  rolling  barrel 
A.  This  tank  should  be  provided  with  trucks,  and  a 
track  should  be  laid  so  that  the  tank  can  be  run  under  the 
rolling  barrel  to  receive  the  prepared  work.  C  is  a  tank 
for  storing  the  prepared  castings  previous  to  further  treat- 
ment, as  hereafter  described ;  D,E,F  and  G  are  divisions  of 
one  common  tank ;  D  is  to  contain  an  alkali  solution,  and 
is  to  be  provided  with  a  steam  coil,  as  shown,  to  heat  the 
solution ;  E  is  a  compartment  for  containing  water  for 
rinsing ;  F  is  to  contain  an  acid  solution ;  G  is  for  the 
muriate  of  zinc ;  H  is  the  roughing  kettle  of  tin ;  K  is  the 
finishing  kettle;  L  is  the  oil  for  cooling  the  work.  The 
arrangement  of  this  tank  was  explained  in  the  chapter  on 
general  tinning ;  M  is  a  wooden  tank  large  enough  to  ac- 
commodate the  iron  tank  L  and.  allow  it  to  be  surrounded 
with  water ;  N  is  a  tank  for  containing  hot  water,  in  which 
the  tinned  work  is  dipped  to  remove  any  traces  of  oil  or 
acid ;  it  is  provided  with  a  steam  coil,  as  shown ;  O  is  a 


GALVANIZING   AND   TINNING. 


•-     --^JB:-  -       -         ' 

E3 


TINNING.  69 

box  to  contain  sawdust  for  drying  off  the  work  when 
it  comes  from  the  hot  water  contained  in  the  tank  N ;  R  R 
is  a  drain  for  carrying  oft  the  waste  water  and  S  S  are 
the  tracks  for  moving  the  tanks  B  and  C ;  T  is  a  tank  for 
containing  a  solution  of  hydrofluoric  acid,  to  be  used  as 
hereafter  described,  and  U  is  a  storage  tank.  It  is  per- 
haps needless  to  say  that  the  ground  plan  may  be  changed 
to  suit  local  conditions. 

Only  the  most  simple  tools  are  required,  which  may 
be  varied  by  the  ingenuity  of  the  operator  to  suit  existing 
conditions  of  work.  We  give  a  sketch  showing  the  most 
common  in  Fig.  13. 

GENERAL  CONSIDERATIONS. 

In  preparing  gray  iron  castings  to  take  a  coating  of 
tin  there  are  several  essential  things  to  be  taken  into  con- 
sideration :  the  quality  of  the  iron,  the  form  of  the  cast- 
ings, their  condition  when  they  come  to  the  tinner,  and  if 
cored,  the  nature  of  the  cores  used. 

Hard  iron  needs  a  longer  preparation  than  soft  iron 
and  a  longer  immersion  in  the  molten  tin.  Castings  that 
are  made  from  patterns  not  designed  with  a  view  to  avoid- 
ing sharp  angles,  in  which  the  molding  sand  can  find  lodg- 
ment, are  much  more  difficult  to  prepare  than  those  made 
from  patterns  free  from  these  obstacles.  It  is,  of  course, 
not  always  possible  to  do  away  with  sharp  angles  in  mak- 
ing patterns  for  castings  that  are  designed  to  be  tinned, 
but  whenever  possible  they  should  be  avoided  in  the  inter- 
est of  easy  cleaning  from  sand  and  perfect  coating  of  the 
work. 

Castings  that  have  been  freed  from  sand  by  the  use  of 
sulphuric  acid  require  a  special  preparation  before  they 
will  take  a  perfect  coating  of  tin,  and  the  use  of  this  acid 


GALVANIZING    AND    TINNING. 


should  be  avoided  if  possible.  Cored  castings  made  with 
cores  in  which  rosin  has  been  used  must  be  treated  dif- 
ferently from  those  made  with  an  oil  or  glue  core.  For 
the  intelligent  understanding  of  the  different  conditions 
we  give  the  specific  course  to  be  followed  in  each  case. 


Fig.  34. — Top  View  of  Rolling  Barrel  with  Receiving  Tank 
in  Position. 

The  perfect  coating  of  gray  iron  requires  the  use  of 
two  tinning  kettles,  and  where  castings  are  to  be  tinned 
previous  to  electroplating  three  kettles  of  tin  should  be 
used  to  insure  the  smoothest  coating  and  the  brightest 
luster. 

TUMBLING   BARREL. 

An  outfit  for  preparing  and  tinning  cast  iron  consists 
of  a  tumbling  barrel,  constructed  in  accordance  with  the 


TINNING. 


plan  shown  by  Figs.   34,  35,  36  and  37.       The  points 
wherein  this  barrel  differs  from  the  ordinary  wet  rolling 


a  a 


gr.  85.— Side  View  of  Fig.  34. 


Fig.  36.— Gear  End  of  Fig.  34. 

barrel  are  that  it  is  built  very  heavy  and  strong.      It  is 
provided  with  valves  for  the  escape  of  the  gases  generated 


72  GALVANIZING   AND    TINNING. 

by  the  chemicals  used,  and  the  opening  where  the  barrel  is 
filled  is  arranged  to  close  tightly. 

For  general  work  we  prefer  a  barrel  48  inches  long 
and  24  inches  in  diameter.  The  shell  we  make  of  ^-inch 
boiler  iron,  and  use  cast  iron  heads  il/2  inches  thick.  The 
manhole  cover  we  make  I  inch  thick,  and  have  it  well 
ribbed  to  give  additional  strength. 

Fig.  34  is  a  top  view  of  the  barrel,  and  it  also  shows 
the  receiving  tank  H,  designated  in  the  ground  plan,  Fig. 
33,  as  B. 

Fig-  35  is  a  side  view  of  Fig.  34,  and  Fig.  36  is  a  view 
of  the  gear  end  of  the  barrel. 

Fig.  37  gives  the  details  of  the  barrel,  in  which  A  is  an 
end  view  of  the  trunnions  B,  and  C  and  D  are  the  pillow 
blocks  supporting  the  barrel  and  E  those  for  the  pinion 
shaft ;  F  is  the  valve  for  the  relief  of  gas  and  G  is  a  view 
of  the  end  of  the  barrel  on  which  the  valves  F  are  placed. 

Two  or  more  kettles  (depending  on  the  nature  of  the 
work)  set  after  the  plan  illustrated  by  Figs.  26,  27  and  28, 
and  various  tanks  built  after  Fig.  12,  complete  the  outfit. 

The  first  operation  in  preparing  the  castings  for  tin- 
ning is  to  free  them  from  sand.  This  is  best  accomplished 
by  the  use  of  the  ordinary  tumbling  barrel,  which  gives 
the  castings  a  smooth  clean  surface  while  doing  the  work 
of  removing  the  sand.  Where  the  castings  are  of  a  na- 
ture to  prevent  their  perfect  cleaning  by  tumbling,  the 
sand  should  be  removed  by  a  solution  of  hydrofluoric  acid 
and  water.  Sulphuric  acid  will  do  the  work,  but  in  a 
much  inferior  manner  and  to  the  injury  of  the  castings  in 
relation  to  their  ready  and  perfect  coating.  The  reason 
for  this  is  easily  understood.  Hydrofluoric  acid  acts  di- 
rectly on  the  sand,  dissolving  it  rapidly  without  attacking 
the  iron  to  any  great  extent.  The  action  of  sulphuric  acid 


TINNING. 


Fig.  37.— Details  of  Rolling  Barrel 


74 


GALVANIZING   AND   TINNING. 


is  the  reverse,  the  iron  being  dissolved  on  the  surface, 
causing  the  sand  to  fall  off,  while  the  sand  itself  is  not 
affected. 

FREEING    GRAY    IRON     CASTINGS    FROM     SAND    BY     HYDRO- 
FLUORIC  ACID. 

While  this  operation  is  nearly  the  same  as  the  one 
given  for  cleaning  malleable  iron  by  the  use  of  this  acid 


DRAIN  PIPE — @ 


Fig.  88. — Detail  of  Floor  Drainage. 

we  wish  to  impress  the  operator  with  the  fact  that  in 
treating  gray  iron  with  acid  of  any  kind,  for  the  purpose 
of  preparing  it  for  tinning,  much  more  care  must  be  ex- 
pended in  the  operation  than  with  malleable  iron,  as  the 
overpickling  of  gray  iron  leaves  the  surface  soft  and 
gummy,  in  which  condition  it  will  not  take  a  coating  of 
tin,  and  it  is  no  easy  matter  to  get  it  in  a  condition  where 
it  will. 

For  quick  cleaning  of  sandy  castings  by  the  use  of 
hydrofluoric  acid  the  preparation  should  be  i  of  acid  to 


TINNING. 


75 


Fig.  39. -Front  View  of  Retinning  Stack. 


Fig.  40.— Back  and  End  View  of  Fig.  39. 


76  GALVANIZING    AND    TINNING. 

20  of  water.  For  slow  cleaning,  which  ic  necessary  on 
castings  having  sharp  angles  into  which  the  molding  sand 
has  burned,  use  the  acid  in  the  proportion  of  i  of  acid  to 
30  of  water.  The  castings  may  remain  in  this  solution 
until  the  sand  is  dissolved,  after  which,  provided  they 
have  not  been  made  with  rosin  cores,  they  are  ready  to  be 
placed  in  the  tumbling  barrel  used  to  prepare  them  for 
tinning.  If  rosin  cores  have  been  used  they  are  to  be 
treated  in  a  special  way,  which  will  be  explained  in  its 
turn. 

A  good  arrangement  to  clean  sandy  castings  with" 
hydrofluoric  acid  is  to  have  two  tanks  (oil  barrels  sawed 
in  half  will  answer),  one  elevated  above  the  other  by 
means  of  a  stand  or  bench,  so  that  the  top  of  the  lower 
tank  will  be  3  or  4  inches  below  the  bottom  of  the  ele- 
vated tank.  Bore  a  hole  in  the  side  of  the  upper  tank 
close  to  the  bottom  and  provide  a  plug.  Place  the  cast- 
ings in  the  upper  tank  and  cover  them  with  the  solution, 
which  has  previously  been  mixed  and  is  contained  in  the 
tank  below.  When  the  castings  have  been  completely 
freed  from  sand  remove  the  plug  and  allow  the  solution  to 
escape  into  the  tank  below,  where  it  remains  until  re- 
quired for  use  again.  No  specific  rule  can  be  given  as  to 
the  time  required  to  clean  the  castings,  and  it  is  not  neces- 
sary, as  an  examination  of  the  work  from  time  to  time 
while  under  treatment  will  determine  when  they  are  clean. 
"Castings  on  which  a  light  sand  is  attached  might  be  clean 
after  15  minutes'  immersion  in  the  solution,  while  castings 
having  a  heavy  coating  of  sand,  or  on  which  the  sand  has 
burned,  might  require  three  or  four  hours. 

If  the  nature  of  the  sand  attached  to  the  castings 
makes  it  seem  probable  that  they  will  require  a  longer  im- 
mersion in  the  acid,  weaken  it  by  adding  water  to  a  point 


TINNING.  77 

where  there  can  be  no  possible  danger  of  the  castings 
being  affected  in  the  way  mentioned  in  the  beginning  of 
this  subject. 

T  and  U  in  Fig.  33  are  the  tanks  designed  for  treat- 
ing the  castings  with  hydrofluoric  acid.  If  it  is  found 
impracticable  to  get  this  acid  the  work  may  be  done  with 
sulphuric  acid,  in  which  case  the  arrangement  for  its  use 
will  occupy  the  same  position  as  designated  for  hydro- 
fluoric acid. 

CLEANING  SANDY  CASTINGS  WITH  SULPHURIC  ACID. 

If  sulphuric  acid  is  used  to  free  the  castings  from  sand 
place  them  on  an  inclined,  raised  platform,  which  platform 
should  be  of  a  size  to  accommodate  the  intended  produc- 
tion and  arranged  to  allow  the  solution  to  flow  back  into 
the  tank  placed  at  the  lowest  point  to  receive  it.  Make  the 
solution  in  the  proportion  of  i  of  acid  to  6  of  water,  and 
keep  the  castings  wet  with  this  solution  until  the  sand  is 
readily  removed  by  the  application  of  water.  Gray  iron 
castings  cleaned  in  this  way  will  have  a  soft,  gummy  de- 
posit on  the  surface,  and  will  not  take  as  perfect  a  coating 
of  tin  as  castings  cleaned  by  dry  tumbling  or  by  the  use 
of  hydrofluoric  acid,  and  they  must  be  given  a  special 
treatment  before  tinning,  which  will  be  described  in  con- 
nection with  the  treatment  for  castings  made  with  rosin 
cores  and  hard  and  greasy  castings. 

After  the  castings  have  been  freed  from  sand  in  some 
one  of  the  ways  described,  provided  they  are  not  exces- 
sively hard  castings  or  made  with  rosin  cores,  are  not 
greasy  or  "  pickled  "  with  sulphuric  acid,  and  have  not 
been  faced  with  black  lead  facing,  then  they  are  ready  for 
tumbling  in  the  solution  of  muriatic  acid,  sal  ammoniac 
and  water.  If  any  of  these  conditions  exist  they  must 


78  GALVANIZING   AND    TINNING. 

be  given  a  treatment  in  a  bath  of  hot  caustic  soda  or 
soda  ash. 

THE  USE  OF  A  HOT  ALKALI  BATH   IN   CERTAIN   CASES. 

If  castings  have  been  overpickled — that  is,  left  in  the 
pickle  until  the  surface  has  become  covered  with  a  soft, 
gummy  substance — or  if  rosin  cores  have  been  used  in  mak- 
ing the  castings  or  black  lead  facing  used  to  give  a 
smooth  surface,  or  if  grease  or  paint  is  present,  they  must 
be  immersed  for  several  minutes  in  a  boiling  solution  of 
caustic  soda  or  soda  ash.  Make  the  solution  very  strong, 
and  see  that  the  strength  is  maintained  by  adding  fresh 
material  as  needed. 

After  this  treatment  the  castings  must  be  thoroughly 
washed  with  clean  water  before  they  are  placed  in  the 
barrel  used  to  prepare  them  for  tinning.  D  in  Fig.  33 
designates  the  tank  to  be  used  for  the  hot  alkali  solution 
and  F  in  the  same  illustration  is  the  tank  used  for  rinsing. 

PREPARING  THE  CASTINGS  IN  THE  GAS  BARREL. 

The  details  of  cleaning  having  been  carefully  attended 
to,  place  the  castings  in  the  tumbling  barrel,  together  with 
a  quantity  of  ordinary  "  stars,"  such  as  are  used  in  dry 
tumbling,  being  careful  to  load  the  barrel  in  such  a  way  as 
to  prevent  breaking  or  wearing  the  corners  of  the  castings. 
Tea  kettles  should  be  filled  full  of  the  stars  or  shot  before 
placing  them  in  the  tumbling  barrel  and  light,  delicate 
castings  should  be  packed  tight  enough  to  prevent  break- 
ing. Stars  or  shot  sufficient  to  fill  the  barrel  about  one- 
fourth  full  will  be  found  the  most  desirable  quantity  for 
ordinary  work,  although  on  hollow  ware  much  more  is 
needed,  or  enough  to  take  up  nearly  all  the  vacant  space. 
After  the  barrel  has  been  loaded  in  the  way  described  put 


TINNING.  79 

in  sufficient  water  to  fill  it  about  three- fourths  full,  then 
add  to  the  barrel  15^  pounds  of  commercial  muriatic  acid 
and  2  pounds  of  gray  granulated  sal  ammoniac.  The 
barrel  is  now  ready  to  be  closed  and  started,  presuming 
that  the  operator  has  examined  the  valves  to  see  that  they 
are  in  perfect  working  order  previous  to  loading  the 
barrel. 

After  the  barrel  has  been  in  motion  from  5  to  15  min- 
utes, depending  on  the  temperature  of  the  water  used, 
there  will  be  formed  sufficient  gas  to  cause  the  valves  to 
open.  The  escape  of  gas  will  be  accompanied  by  quanti- 
ties of  the  solution,  and  the  end  of  the  barrel  on  which 
the  valves  are  placed  should  be  inclosed,  unless  the  barrel 
is  set  up  in  a  different  room  from  the  rest  of  the  outfit. 

The  time  that  the  castings  should  be  rolled  in  this  solu- 
tion varies  from  two  and  one-half  to  five  hours.  Soft 
smooth  castings  will  take  a  nice  coating  after  a  prepara- 
tion of  two  and  one-half  hours,  while  to  obtain  the  same 
results  on  hard  iron,  iron  cleaned  by  the  use  of  sulphuric 
acid,  hollow  ware  and  tea  kettles  and  castings  having  a 
black  lead  facing,  five  hours  in  the  barrel  are  necessary. 
It  is  safe  to  say  that  three  and  one-half  hours  will  properly 
prepare  ordinary  castings,  the  barrel  making  40  revolu- 
tions a  minute.  For  hollow  ware,  tea  kettles  and  very 
delicate  castings  the  barrel  should  not  attain  a  speed  of 
over  30  revolutions  per  minute.  After  the  castings  have 
been  rolled  in  the  solution  the  required  time  open  the 
barrel  and  cover  its  contents  with  water  immediately. 
Do  not  let  any  time  be  wasted  in  getting  the  castings  cov- 
ered with  water,  as  a  slight  exposure  to  the  air  will  cause 
them  to  oxidize  and  prevent  them  from  taking  the  tin. 
If  the  castings  are  properly  prepared— that  is,  if  they 
have  been  rolled  in  the  solution  long  enough — they  will  be 


80  GALVANIZING   AND   TINNING. 

in  such  a  condition  after  rinsing  that  they  will  not  soil  a 
white  cloth  to  any  extent. 

As  soon  as  the  operator  has  determined  whether  the 
castings  will  tin  properly  (which  is  done  by  putting  one  or 
two  of  the  pieces  through  the  regular  treatment)  he  will 
proceed  to  dump  the  contents  of  the  barrel  into  the  receiv- 
ing tank,  located  directly  under  the  barrel.  This  tank  is 
designated  in  Fig.  33  as  B,  and  should  contain  about  one- 
third  more  cubic  feet  than  the  rolling  barrel.  From  this 
receiving  tank  the  castings  should  be  removed  to  the  stor- 
age tank  designated  C  in  Fig.  33.  A  good  sized  coke 
fork  is  best  for  handling  the  castings  from  tank  to  tank 
as  it  lets  the  shot  or  stars  fall  to  the  floor  and  separate 
from  the  castings. 

In  placing  the  castings  in  the  storage  tank  care  should 
be  taken  to  have  those  with  depressions  or  cavities  go 
under  the  water  with  the  depressions  or  cavities  up.  In 
other  words  castings  of  a  shape  that  would  admit  of  a 
particle  of  air  being  retained  should  be  so  placed  that  no 
air  will  be  retained.  If  this  occurs  there  will  be  a  rusty 
place  form  on  the  casting  to  which  the  tin  will  not  adhere. 
Should  it  be  found  that  the  castings  are  not  properly  pre- 
pared the  barrel  should  be  recharged  by  adding  6  pounds 
of  muriatic  acid  and  allowed  to  run  about  an  hour  longer. 

The  important  point  to  be  kept  in  mind  in  preparing 
cast  iron  for  tinning  is  that  the  surface  of  the  iron  must 
be  made  perfectly  clean.  Not  only  clean  from  sand  and 
rust,  but  from  every  foreign  substance.  It  may  seem  to 
the  reader  that  we  are  dwelling  on  this  point  unneces- 
sarily, but  only  by  the  most  careful  attention  to  the  proper 
preparation  of  the  castings  and  in  keeping  them  in  the 
same  clean  condition  until  they  receive  the  first  coat  of  tin 
can  perfectly  satisfactory  work  be  obtained. 


TINNING.  8.1 

If  the  iron  is  allowed  to  roll  in  the  solution  too  long  a 
time  the  surface  becomes  soft  from  the  action  of  the  acid, 
and  the  tin  will  not  take.  The  same  trouble  will  be  ex- 
perienced if  the  solution  in  the  rolling  barrel  is  too  strong, 
or  if  the  castings  are  allowed  to  remain  in  the  solution 
too  long  after  they  are  rolled.  In  rolling  the  castings  cal- 
culation should  be  made  to  complete  the  work  before  the 
stopping  of  the  power  at  noon  and  night.  Three  and  one- 
half  hours  being  required  on  an  average  to  prepare  most 
iron  in  the  rolling  barrel,  it  is  easy  to  arrange  to  start  the 
barrel  in  time  to  complete  one  batch  in  the  morning  and 
one  in  the  afternoon.  This  would  furnish  work  enough 
to  keep  two  hands  engaged,  although  one  set  of  kettles 
would  take  care  of  all  the  iron  that  could  be  prepared  in 
a  barrel  the  size  we  show — viz.,  2  feet  in  diameter  by  4 
feet  in  length. 

If  the  castings  are  quite  soft  and  clean  three  batches 
may  be  prepared  in  ten  hours,  in  which  case  the  second 
batch  should  be  in  the  barrel  in  time  to  give  it  at  least 
one  hour's  rolling  before  the  power  is  stopped  at  noon. 
When  a  batch  of  iron  is  left  in  the  barrel  during  the  noon 
hour,  leave  the  barrel  closed,  and  in  a  position  where  one 
of  the  valves  will  be  up  or  the  opening  above  the  solution 
in  the  barrel.  Unless  this  is  done  the  valves  may  open 
and  allow  the  solution  to  escape,  necessitating  recharging 
the  barrel.  If  the  batch  is  not  completed  in  season  to 
remove  it  to  the  storage  tank  before  the  time  for  stopping 
the  power  at  night,  remove  the  cover,  and  allow  enough 
fresh  water  to  flow  into  the  barrel  to  displace  at  least  half 
of  the  solution,  and  leave  it  in  that  condition  until  morn- 
ing, taking  care  that  the  valves  do  not  leak,  that  the  iron 
is  completely  covered,  and  that  the  water  is  not  left  run- 


82  GALVANIZING   AND   TINNING. 

ning,  as  iron  will  rust  in  running  water  even  if  the  water 
covers  it. 

In  rolling  a  batch  of  iron  it  will  often  be  found  that 
a  black  foam  will  rise  to  the  surface  of  the  solution  when 
the  barrel  is  opened.  This  is  from  the  iron  dust  left  on 
castings  that  are  cleaned  by  dry  tumbling,  and  it  will  also 
be  found  in  preparing  castings  that  have  been  faced  with 
foundry  facing  of  any  sort.  When  this  foam  or  scum 
is  present,  let  water  flow  into  the  barrel,  with  the  opening 
in  such  a  position  as  to  allow  the  objectionable  matter  to 
pass  off.  The  first  one  or  two  batches  prepared  in  a  new 
barrel  are  liable  to  give  trouble  in  tinning  unless  the  in- 
side of  the  barrel,  with  the  shot  to  be  used,  is  cleaned  with 
a  strong  alkali  solution.  The  simplest  way  is  to  put  the 
shot  into  the  barrel,  and  after  filling  it  about  half  full  of 
strong,  hot  alkali  solution,  close  the  barrel,  and  allow  it 
to  run  an  hour  or  more,  after  which  the  interior  of  the 
barrel  and  the  shot  used  should  be  rinsed  with  plenty  of 
clean  water. 

Where  castings  are  tinned  for  the  purpose  of  electro- 
plating them  it  is  desirable,  if  an  extra  smooth  surface  is 
desired,  to  give  them  a  rolling  in  gravel  and  water  in  the 
ordinary  wet  rolling  barrel,  although  this  treatment  is 
not  necessary  in  order  to  prepare  them  to  take  a  coating 
of  tin.  In  treating  castings  in  this  way  use  a  coarse  hard 
gravel,  and  some  castings  may  be  rolled  20  to  30  hours 
to  good  advantage  if  the  barrel  is  properly  loaded. 

It  sometimes  happens  that  castings  are  encountered 
that  have  a  ground  work  of  delicate  design  into  which 
the  sand  has  burned.  If  such  are  placed  in  the  rolling 
barrel  with  a  good  quantity  of  shot  and  given  two  or 
three  hours'  rolling  in  a  solution  of  hydrofluoric  acid  and 
water,  i  part  acid  to  75  or  100  of  water,  they  will  be 


TINNING.  83 

cleaned  very,  nicely.  Where  this  is  done  let  the  hydro- 
fluoric solution  run  out  of  the  barrel  before  charging  it 
with  the  regular  solution  of  muriatic  acid,  sal  ammoniac 
and  water. 

The  operator  must  bear  in  mind  at  all  times,  as  a  safe- 
guard against  accident,  that  he  must  see  that  the  valves 
on  the  rolling  barrel  are  in  working  order  previous  to 
loading  the  barrel.  These  valves  should  be  adjusted  to 
open  at  a  pressure  of  40  pounds.  If  by  reason  of  a  leak 
in  an}-  part  in  the  barrel  gas  is  not  generated  the  work 
will  not  tin  properly.  Do  not  approach  the  barrel  with  a 
light  at  any  time  when  the  gas  is  escaping,  or  at  any  time 
when  the  gas  is  being  generated  in  the  barrel.  If  after 
stopping  the  barrel  it  is  found  that  the  valves  leak,  as 
they  may  from  becoming  clogged,  stop  the  leak,  as  the 
solution  will  escape,  allowing  the  work  to  oxidize.  Badly 
oxidized  castings  will  not  tin.  The  solution  contained 
in  tank  F,  Fig.  33,  is  calculated  to  remove  a  light  oxide, 
but  castings  that  are  heavily  oxidized  must  be  rerolled. 

COATING    THE    CASTINGS    WITH    TIN. 

The  tin  in  the  kettles  being  at  the  proper  heat  for  the 
work  in  hand,  as  specified  later  on,  the  operator  takes  a 
small  quantity  of  the  castings  from  the  storage  tank  C, 
Fig.  33,  and  places  them  in  the  wire  basket  designated  A 
in  Fig.  13,  taking  care  to  place  those  having  concave  sides, 
holes  or  depressions  so  that  none  of  the  various  solutions 
through  which  they  are  now  to  pass  will  be  retained. 
The  castings  contained  in  the  wire  basket  must  now  be 
immersed  in  the  solution  of  caustic  soda  or  potash,  re- 
ferred to  in  connection  with  the  treatment  for  greasy, 
hard  or  lead  faced  castings,  which  solution  is  contained  in 
tank  D,  Fig.  33.  This  solution  must  be  kept  at  the  boil- 


84  GALVANIZING  AND   TINNING. 

ing  point,  and  from  one  to  two  minutes  is  sufficient  time 
to  leave  the  castings  in.  The  best  plan  for  heating  this 
solution  is  to  have  a  steam  coil  in  the  bottom  of  the  tank, 
as  shown  in  the  illustration,  and  to  allow  the  exhaust  steam 
to  pass  into  the  rinsing  tank,  which  is  placed  directly  be- 
side it,  as  shown  in  the  ground  plan.  The  rinsing  tank 
is  designated  E  in  Fig.  33.  After  the  castings  have  stood 
in  the  alkali  bath  contained  in  tank  D  the  desired  time 
they  are  placed  in  the  rinsing  tank  E  until  all  traces  of 
that  solution  are  removed.  This  will  take  the  fraction  of 
a  minute  provided  a  stream  of  water  is  kept  flowing  into 
the  tank,  as  it  should  be. 

The  next  move  is  to  immerse  the  castings  in  a  very 
weak  solution  of  muriatic  acid  and  water,  I  part  acid  to 
40  of  water.  The  castings  must  not  be  allowed  to  stand 
in  this  solution  more  than  two  or  three  seconds.  The  tank 
to  contain  this  solution  is  designated  as  F  in  Fig.  33. 

Next  place  the  castings  in  the  tank  G,  Fig.  33,  which 
contains  muriate  of  zinc,  to  which  has  been  added  5 
pounds  of  gray  granulated  sal  ammoniac  for  every  gallon 
of  the  muriate.  Muriate  of  zinc  is  made  by  dissolving 
zinc  in  muriatic  acid,  allowing  the  acid  to  dissolve  all  the 
zinc  it  will.  For  the  purpose  of  making  this  cut  acid  an 
earthen  crock  can  be  employed,  or  an  oil  barrel  sawed  in 
half  will  answer  the  purpose. 

The  castings  are  now  ready  to  be  immersed  in  the 
molten  tin  contained  in  the  first  kettle  and  shown  in  Fig. 
33  at  H.  The  tin  in  this  kettle  should  attain  a  heat  of 
500  degrees  F.,  and  this  heat  should  be  maintained  during 
the  time  the  kettle  is  in  use. 

Before  immersing  the  castings  in  this  kettle  the  sur- 
face of  the  tin  should  be  covered  by  a  flux  made  by  boil- 
ing a  quantity  of  the  muriate  of  zinc  on  top  of  the  molten 


TINNING.  85 

tin,  and  adding  quickly  to  the  boiling  mass  a  quantity 
of  white  granulated  sal  ammoniac.  The  sal  ammoniac 
must  be  added  by  sprinkling  it  on  before  the  acid  is  evap- 
orated by  the  heat  of  the  tin.  It  will  take  a  little  time 
and  experience  before  the  proper  consistency  of  this  flux 
can  be  attained.  The  proper  combination  of  this  flux 
is  one  of  the  most  essential  points  in  the  successful  coat- 
ing of  the  cast  iron  in  this  first  kettle  of  tin.  If  the  flux 
is  allowed  to  become  hard  and  dry,  as  it  soon  will  by  con- 
tinued use  unless  careful  and  constant  attention  is  given 
to  it,  the  flux  will  adhere  to  the  castings  as  they  pass 
through  it  into  the  tin  below,  and  thereby  prevent  them 
from  coating. 

When  it  is  found  that  the  flux  is  becoming  thick  and 
lumpy  add  a  sufficient  quantity  of  the  muriate  of  zinc  and 
powdered  sal  ammoniac  to  cause  the  flux  to  boil  up  to  a 
depth  of  y2  inch  or  more.  When  this  result  is  obtained 
take  a  perforated  iron  skimmer  and  carefully  remove  any 
hard  lumps  and  congealed  matter  remaining  in  the  flux, 
allowing  such  as  readily  pass  through  the  skimmer  to  re- 
main in  the  kettle.  The  purpose  of  this  flux  is  to  pre- 
vent the  surface  of  the  tin  from  becoming  oxidized  by 
exposure  to  the  air,  and  also  to  prevent  the  hot  metal 
from  spattering  and  burning  the  operator  when  the  wet 
castings  come  in  contact  with  the  tin.  Keep  carefully  in 
mind  that  this  flux  must  at  all  times  be  kept  in  a  thin 
liquid  condition,  otherwise  the  succeeding  operations 
through  which  the  castings  are  to  pass  before  they  are 
completed  will  be  unsuccessful. 

In  placing  the  castings  in  this  first  kettle  of  tin  care 
should  be  taken  to  get  them  immersed  as  soon  as  possible. 
If  they  are  allowed  to  float  on  the  suriace  of  the  tin  the 
muriate  of  zinc  with  which  they  are  wet  (for  the  purpose 


86  GALVANIZING   AND   TINNING. 

of  causing  the  tin  to  adhere)  will  dr.y  off,  and  the  tin  will 
not  adhere  to  that  part  of  the  casting  left  exposed.  The 
work  must  be  kept  below  the  surface  of  the  tin  until  it 
has  become  as  hot  as  the  tin  itself,  and  until  the  tin  has 
ceased  to  bubble  or  to  be  agitated  by  the  castings  that  are 
immersed.  This  boiling  or  agitation  will  cease  when  the 
air  is  expelled  from  the  iron  and  the  flux  that  adhered  to 
it  as  it  passed  through  has  risen  to  the  surface  of  the  tin 
again. 

The  proper  way  to  immerse  the  work  in  this  first  ket- 
tle of  tin  is  to  rest  the  handle  of  the  basket  containing  it 
on  the  edge  of  the  tin  kettle,  elevating  the  basket  at  an 
angle  that  will  prevent  it  touching  the  molten  tin  until  the 
operator  is  ready  to  have  it.  Cant  the  basket  so  that  one 
of  the  lower  corners  will  enter  the  tin  first ;  in  other  words, 
do  not  allow  the  bottom  of  the  basket  to  come  directly  onto 
the  surface  of  the  tin,  as  the  effect  of  having  so  much  wet 
metal  as  the  bottom  of  the  basket  presents  come  in  con- 
tact with  the  molten  tin  will  be  an  explosion,  resulting 
most  likely  in  the  serious  injury  of  the  operator  or  any 
one  standing  near.  When  the  basket  is  in  the  described 
position  lower  it  carefully  until  i  inch  or  2  inches  of  the 
bottom  and  one  side  is  immersed  in  the  tin,  then  lower 
rapidly,  but  steadily,  until  the  basket  and  its  contents  are 
completely  immersed. 

At  this  point  turn  the  basket  completely  over,  bottom 
up,  and,  using  the  edge  of  the  tin  kettle  as  a  rest  for  the 
handle,  lift  the  basket  from  the  tin.  When  the  basket  is 
free  turn  it  bottom  down  and  use  it  in  that  position  to 
keep  the  castings  it  contained  below  the  surface  of  the  tin. 
Fill  the  kettle  as  full  of  castings  as  it  will  hold  and  allow 
them  to  be  completely  immersed.  Several  of  the  wire 


TINNING.  7 

baskets  may  be  employed  to  insure  having  a  batch  ready 
to  immerse  when  the  previous  one  is  disposed  of. 

It  sometimes  happens  that  the  operator  carelessly  omits 
dipping  the  work  in  the  cut  acid  contained  in  tank  G,  Fig. 
33 ;  that  is,  he  may  attempt  to  immerse  the  work  in  the 
molten  tin  directly  from  tank  D,  E  or  F.  Such  neglect  is 
dangerous  and  likely  to  be  attended  with  serious  results  to 
the  operator,  from  the  hot'metal  spattering. 

There  are  many  kinds  of  work  that  may  be  strung  on 
wires  and  handled  through  the  different  stages  without 
the  use  of  the  wire  baskets.  When  wires  are  used  the 
shape  may  be  varied  to  suit  conditions.  While  we  show 
the  most  common  in  Fig.  13,  the  ingenuity  of  the  operator 
must  be  employed  in  selecting  those  best  adapted  to  his 
wants  and  in  devising  others  for  himself. 

The  kettle  being  full  as  described,  the  castings  must 
remain  where  they  are  from  5  to  15  minutes,  or  until  they 
have  taken  a  perfect  coating  of  tin.  If  in  this  time  they 
are  not  properly  coated,  some  error  has  been  committed  in 
the  previous  operations  and  the  work  must  be  rerolled. 

What  dross  or  slag  forms  in  a  tin  kettle  rises  to  the 
surface.  A  considerable  part  of  this  objectionable  matter 
will  be  found  in  the  first  kettle,  which  must  be  removed 
before  the  work  can  be  carried  to  the  finishing  kettle  or 
kettles.  To  accomplish  the  removal  of  this  dross  or  slag, 
floating  on  the  surface  of  the  tin,  use  a  perforated,  concave 
iron  skimmer.  The  holes  in  the  skimmer  should  be  large 
enough  to  allow  the  clear  tin  to  flow  through  freely,  and 
care  should  be  taken  not  to  waste  the  flux  in  skimming  out 
the  dross.  If  the  skimmer  is  canted  edgewise  as  soon  as 
the  clear  tin  passes  off  the  slag  will  adhere  to  the  skimmer 
and  the  flux  will  flow  back  into  the  kettle. 

When  all  the  slag  has  been  removed  grasp  one  of  the 


88  GALVANIZING    AND    TINNING. 

castings  with  a  pair  of  tongs  and  remove  it  with  a  quick 
motion  from  the  tin.  .If  wires  have  been  employed  and 
the  work  is  strung,  take  one  or  more  wires  and  remove  in 
the  same  way  to  the  next  kettle,  taking  care  that  no  flux  or 
dross  is  carried  along  with  the  work.  The  temperature 
of  the  tin  in  the  first  kettle  is  much  too  high  for  finishing 
the  work,  and  when  the  castings  that  are  taken  from  this 
first  kettle  are  exposed  to  the  air  they  will  be  more  or  less 
yellow,  depending  on  the  heat  of  the  tin.  A  bright  yellow 
or  golden  color  indicates  too  high  a  heat  of  the  tin  and 
must  be  avoided.  A  slight  yellowish  tinge  indicates  the 
proper  heat. 

The  tin  in  the  second  kettle,  which  is  designated  in  Fig. 
33  as  K,  and  which  is,  in  most  cases,  the  finishing  kettle, 
must  be  maintained  at  a  temperature  of  about  400  degrees 
F.,  and  the  surface  kept  covered  to  the  depth  of  from  y2  to 
i  inch  with  pure  beef  tallow.  Palm  oil  may  be  introduced 
into  the  tallow  with  good  results,  using  of  the  latter  about 
10  per  cent.  The  operator  retains  the  castings  held  by  the 
tongs  or  wires  immersed  in  this  second  kettle  one  or  two 
seconds  and  then,  with  the  tongs  held  in  the  left  hand,  he 
removes  the  piece  from  the  tin.  As  soon  as  the  piece  is 
clear  of  the  tin  the  operator  grasps  it  with  a  pair  of  tongs 
held  in  the  right  hand,  and  with  a  few  rapid  swinging 
motions  to  free  the  article  from  surplus  tin,  he  plunges  it 
into  a  tank  containing  kerosene  oil.  If  wires  are  being 
employed  he  swrings  the  work  to  and  fro  rapidly  to  free  it 
from  the  surplus  tin,  and  when  plunging  it  into  the  oil  he 
must  give  the  work  a  motion  calculated  to  prevent  the 
articles  in  contact  from  adhering  to  each  other. 

The  tank,  which  is  designated  in  Fig.  33  as  L,  in  con- 
nection with  a  companion  tank  M,  should  be  of  sheet  iron 
and  placed  in  the  companion  tank  M  with  a  view  to  having 


TINNING.  89 

a  body  of  water  surrounding  it  to  keep  the  oil  from  becom- 
ing heated,  as  it  soon  would  be  from  the  hot  castings 
constantly  immersed  in  it.  The  work  must  be  immersed 
in  this  oil  long  enough  to  set  the  tin  and  then  immersed  in 
the  cold  water  contained  in  the  companion  tank  M. 

If  the  tin  in  this  last  or  finishing  kettle  is  at  the  right 
temperature  the  work  will  be  white  and  have  a  nice  luster 
after  it  is  cooled.  If  the  work  is  rough  and  lumpy  it  indi- 
cates that  the  tin  in  the  finishing  kettle  was  not  hot  enough 
or  that  the  work  was  kept  in  the  air  too  long  a  time  before 
dipping  it  in  the  oil.  The  tin  in  the  finishing  kettle 
requires  very  little  fire  to  be  maintained  as  there  will  be 
nearly  enough  heat  in  the  castings  when  they  come  from 
the  first  kettle  to  keep  the  tin  in  the  second  at  a  proper 
heat.  If  the  work  is  yellow  after  cooling  in  the  oil,  it  may 
indicate  too  high  a  heat  in  the  finishing  kettle,  or  it  may 
indicate  that  the  casting  was  not  kept  in  the  finishing  ket- 
tle long  enough  to  bring  the'heat  that  the  casting  attained 
in  the  first  kettle  down  to  a  point  where  the  tin  would  not 
be  yellow. 

The  work  will  come  out  of  the  finishing  kettle  smoothly 
and  brightly  coated  even  when  the  temperature  of  that 
kettle  is  so  low  that  if  a  piece  of  cold  iron  be  put  in  the  tin 
would  adhere  to  it  in  a  mass.  The  heat  the  castings  attain 
in  the  first  kettle  makes  it  possible  to  run  the  finishing 
kettle  at  a  very  low  temperature  and  it  is  desirable  to  do  so 
on  very  heavy  castings.  Light  castings  require,  of  course, 
that  a  much  higher  heat  be  maintained  in  the  finishing- 
kettle  than  is  necessary  on  heavy  castings.  The  reason  is 
apparent :  Light  castings  must  be  exposed  to  the  air  a  few 
seconds  while  the  operator  is  switching  off  the  surplus  tin, 
and  being  light,  they,  of  course,  do  not  hold  the  heat  long 


90  GALVANIZING    AND    TINNING. 

enough  to  allow  the  surplus  tin  to  be  shaken  off  without 
leaving  rough,  ragged  edges. 

A  great  deal  of  ingenuity  can  be  displayed  by  the 
operator  in  handling  castings  of  various  shapes  in  such  a 
way  that  no  lumps  or  bunches  of  tin  will  remain  on  the 
work  after  it  is  cooled.  For  example,  in  grasping  the 
article  to  be  cooled  care  should  be  used  to  find  what  part 
of  the  casting  is  best  adapted  to  be  taken  hold  of  by  the 
cooling  tongs  without  marks  of  the  tongs  being  left  after 
the  article  is  cooled.  The  tongs  used  for  cooling  should 
never  be  put  into  the  tin  kettle,  as  the  heat  of  the  casting 
would  cause  it  to  adhere  to  the  tongs  if  they  were  tinned. 
After  shaking  off  the  surplus  tin  change  the  position  of 
the  casting  so  that  the  drop  of  tin,  which  will  naturally  col- 
lect at  the  lowest  point,  will  flow  back  onto  the  casting  and 
dip  in  the  oil  at  once  when  this  is  accomplished. 

A  "  switching  box "  should  be  employed  when 
"  strung  "  work  is  being  handled  to  catch  the  tin  that  is 
thrown  frorh  the  work  in  the  operation  of  "  switching  " 
it  to  throw  off  the  surplus  tin.  This  box  is  a  very  simple 
arrangement.  Its  position  when  in  use  is  designated  D, 
Fig.  25.  Cover  the  interior  of  the  box  with  heavy  paper, 
as  the  hot  tin  will  stick  to  the  wood  unless  paper  is  used. 
The  tin  thus  collected  may  be  thrown  into  the  kettle 
together  with  the  paper  when  the  tin  is  needed  for  use. 

When  the  castings  have  been  finally  cooled  as  already 
described,  they  should  be  immersed  in  a  tank  of  boiling 
water  to  free  them  from  oil  and  also  to  remove  any  trace 
of  acid  that  may  be  on  them.  This  final  rinsing  tank  is 
designated  N  in  Fig.  33.  The  water  must  be  kept  clean 
and  at  the  boiling  point  at  all  times  when  in  use.  An 
ordinary  foundry  riddle  with  upright  handles  long  enough 
to  allow  the  operator  to  set  the  riddle,  with  the  work  to  be 


TINNING.  91 

treated,  into  the  tank  without  scalding  his  hands,  may  be 
employed  to  immerse  the  work  in  this  tank. 

The  castings  should  be  dried  off  in  clean  dry  sawdust, 
and  for  this  purpose  use -sawdust  made  from  pine  or  some 
soft  wood,  as  hardwood  sawdust  will  scratch  the  tinned 
surface.  The  drying  box  is  shown  at  O  in  Fig.  33. 

When  three  kettles  of  tin  are  employed,  as  they  may  be 
to  good  advantage  in  tinning  work  that  is  designed  to  be 
plated,  the  second  kettle  must  be  run  at  a  temperature  of 
450  degrees  F.  The  surface  of  the  tin  in  this  kettle  must 
be  kept  covered  with  an  acid  and  sal  ammoniac  flux  the 
same  as  the  first  kettle.  The  castings  in  the  first  kettle  are 
to  be  passed  in  quantities  to  the  second  kettle,  there  to  re- 
main until  the  first  kettle  is  refilled.  The  same  care  must 
be  taken  not  to  allow  any  of  the  slag  or  flux  that  accumu- 
lates on  the  first  kettle  passing  with  the  work  to  the  second 
kettle,  and  the  tin  in  the  second  kettle  must  be  kept  free 
from  slag. 

The  tin  in  the  third  or  finishing  kettle  should  be  main- 
tained at  a  temperature  of  400  degrees  F.,  and  the  depth 
of  the  tallow  increased  to  3  or  4  inches. 

If  three  kettles  are  employed  they  should  be  square  or 
round  and  arranged  to  fire  from  one  side,  instead  of  at 
the  ends. 

The  water  in  storage  tank  C,  Fig.  33,  will  in  a  short 
time  become  charged  with  the  acid  solution  from  the  roll- 
ing barrel  unless  it  is  changed  frequently.  If  much  acid 
is  present  in  the  water  it  will  impair  the  alkali  solution 
into  which  the  castings  pass  directly  from  the  storage 
tank.  If  a  few  pounds  of  the  alkali  selected  for  use 
(caustic  soda  or  soda  ash) is  added  two  or  three  times  a 
week  the  alkali  will  do  its  work  properly  for  some  time, 
although  it  is  best  to  clean  out  the  tank  and  make  the  solu- 


92  GALVANIZING   AND   TINNING. 

tion  up  fresh  once  in  two  weeks  where  it  is  in  constant 
use. 

In  rinsing  the  castings  in  tank  E,  Fig.  33,  do  not  let 
them  remain  in  a  great  length  of  time  if  water  is  flowing 
in,  as  iron  will  soon  rust  in  running  water.  The  solution 
in  tank  F,  Fig.  33,  should  be  made  up  fresh  after  2  or 
3  tons  of  iron  has  passed  through  it,  and,  as  already  stated, 
the  castings  should  not  be  allowed  to  stand  in  this  solution 
more  than  two  or  three  seconds. 

The  solution  of  muriate  of  zinc  contained  in  tank  G, 
Fig.  33,  should  be  deep  enough  to  cover  the  castings  con- 
tained in  the  wire  basket  used  to  immerse  them  in  the 
first  kettle,  and  the  solution  should  be  kept  in  good  con- 
dition— that  is,  care  should  be  taken  not  to  allow  it  to  be 
weakened  to  any  great  extent  by  the  solution  in  tank  F 
passing  into  it  with  the  work.  The  tank  containing  this 
muriate  of  zinc  should  be  lead  lined  and  an  inner  lining 
of  wood  used  to  protect  the  lead  lining. 

As  it  is  almost  impossible  to  make  castings  that  have 
been  imperfectly  coated  at  the  first  attempt  take  a  satis- 
factory coating  of  tin,  the  operator  should  give  careful 
attention  to  details. 

It  is  possible  by  practice  to  keep  the  tin  at  a  proper 
heat,  but  the  operator  will  find  more  difficulty  in  doing 
this  than  any  other  one  thing  in  the  entire  operation.  That 
the  proper  heat  be  maintained  is  very  essential,  for  if  it  is 
not,  all  previous  care  in  preparing  the  iron  will  have  been 
in  vain.  If  too  hot  the  flux  on  the  first  kettle  of  tin  will 
evaporate  or  burn  off,  and  the  tin  will  not  take  to  the  iron. 
If  too  high  a  heat  is  reached  on  the  kettle  containing  the 
tallow,  tl.e  tallow  will  be  set  on  fire.  As  a  help  to  a  nov- 
ice and,  in  fact,  to  an  experienced  man,  we  recommend 
the  use  of  a  pyrometer,  one  for  each  kettle.  The  expense 


TINNING.  93 

of  providing  them  is  not  to  be  considered  in  comparison 
with  the  advantages  obtained. 

The  kettles  for  containing  the  tin  may  be,  and  usually 
are,  of  cast  iron,  although  fire  box  steel  is  often  employed 
to  make  oblong  kettles. 

A  floor  space  of  20  x  40  feet  will  accommodate  a  tin- 
ning plant  running  two  rolling  barrels.  If  possible,  the 
plant  should  be  located  handy  to  power  and  with  a  view 
to  obtaining  easy  and  perfect  drainage.  If  necessity  com- 
pels the  setting  up  of  the  plant  in  the  factory  building 
above  the  ground  floor,  as  is  sometimes  the  case,  the  floor 
of  the  tinning  room  must  be  so  constructed  that  leakage 
into  the  room  or  rooms  below  will  be  prevented. 

The  dross  or  slag  formed  in  the  kettles  should  be 
stored  away  until  a  sufficient  amount  is  accumulated  to 
make  profitable  the  remelting  of  the  slag  for  the  purpose 
of  reclaiming  what  pure  tin  is  in  it.  For  the  purpose  of 
remelting  this  dross  the  pure  tin  can  be  removed  from 
the  kettle  H,  Fig.  33,  and  the  dross  melted  up  in  it.  When 
the  entire  mass  is  in  a  molten  state,  and  at  a  temperature 
of  about  550  degree  F.,  bail  off  the  liquid  tin  into  cast 
iron  pans  provided  for  that  purpose,  and  what  "dross  re- 
mains into  separate  pans.  This  tin  dross  has  a  market 
value  of  from  40  to  50  per  cent,  of  the  price  of  pure  tin. 

With  the  addition  of  tanks  for  containing  acids  a 
plant  built  to  tin  cast  iron  is  adapted  to  all  descriptions 
of  tinning,  except  redlining  of  tinware  and  the  tinning  of 
sheets. 


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